Forensics midterm

Are fingerprints unique?

-"Uniqueness is commonly assumed." -Are their 2D representations (e.g. on paper) unique? -There is a reduction of information in a projection -Identical twins have same DNA, different fingerprints! -Each person has one DNA composition, but different prints on two thumbs -There are so many people alive today, and not that many places for information on a print -Couldn't it be that by chance two fingerprints are so similar we cannot tell them apart?

The History of Forensic Science - most recent

-2009: NAS report is published -2016: PCAST report is published -Both raise questions about the scientific foundation of forensic disciplines

Mayfield case

-3/11: Bombings in Madrid commuter train -3/13: Interpol requests FBI help to identify print on plastic bag with detonators -3/20: FBI matches print to Brandon Mayfield, Oregon lawyer and recent muslim convert. Mayfield's own fingerprint analyst also said match -4/13: Spanish National Police disagrees with FBI conclusion -5/6 Mayfield arrested by FBI -5/19: Spanish National Police match print to Algerian suspect, Daoud Ouhnane -5/23: FBI admits error. Mayfield is released and later given $2 million

Not even DNA gives total certainty about a "match"

-A "match" is not perfect: We don't know with 100% certainty that a person was the source of the DNA -But we know how likely it is that you'd mistakenly identify someone

Car accident DNA question

-A car accident (a 10 year old lost his two legs) -The owner of the car admits to having a small car accident -After he has been told about the child he claimed that his friend drove the car -The friend is a convicted felon -"The friend asked me to take the blame on me, I didn't know he hit a child" -Who drove the car when the accident occurred? -What should be tested for DNA? -The steering wheel can have the DNA of multiple drivers → does not answer the question -The air-bags open only at the time of the accident -The air-bag was tested and the saliva found on it matched the DNA of the friend of the owner of the car

National Commission on Forensic Science

-A federal advisory committee formed in 2013 through a partnership between the Obama administration and the National Institute of Standards and Technology (NIST) -The Commission's mission is to "enhance the practice and improve the reliability of forensic science." Under Trump administration, Attorney General Jeff Sessions "orders Justice Dept. to end forensic science commission, suspend review policy" -The objectives and scope directed the Commission to provide recommendations and advice to the DOJ concerning national methods and strategies for the following: 1) Strengthening the validity and reliability of the forensic sciences (including medico-legal death investigations) 2) Enhancing quality assurance and quality control in forensic science laboratories and units 3) Identifying and recommending scientific guidance and protocols for evidence seizure, testing, analysis, and reporting by forensic science laboratories and units 4) Identifying and assessing other needs of the forensic science communities to strengthen their disciplines and meet the increasing demands generated by the criminal and civil justice systems at all levels of government

Latent print examination process: ACE-V

-ACE-V: Conventional procedure for associating impressions of friction ridge skin by a latent print examiner involves four phases known as Analysis, Comparison, Evaluation, and Verification (ACE-V) -It has been described in forensic literature as a means of comparative analysis of evidence since 1959 -Analysis: refers to an initial phase in which the examiner studies the unknown print to assess the quality and quantity of relevant detail present -Comparison: is the side-by-side observation of the friction ridge detail in the two prints to visually determine the agreement or disagreement in the details (shape, delta location, shapes of ridges, etc.). -Evaluation: is where the examiner assesses the agreement or disagreement of the information observed during Analysis and Comparison and forms a conclusion -Verification: in some agencies is a review of an examiner's conclusions

Analysis

-After considering the details and the distortion, the examiner judges whether the impression is suitable for a comparison -If the examiner concludes that the print lacks sufficient detail for a comparison, then the examination ends with the determination that the latent print is not suitable for a comparison -Otherwise, the examination moves into the Comparison phase

Aftermath of Mayfield case

-Although some Automated Fingerprint Identification Systems (AFIS) permit fully automated identification of fingerprint records related to criminal history (e.g., for screening job applicants), the assessment of latent prints from crime scenes is based largely on human interpretation -The FBI Laboratory adopted requirements to conduct, in certain cases, "independent application of ACE to a friction ridge print by another qualified examiner, who does not know the conclusion of the primary examiner." -In particular, the FBI Laboratory uses blind verification in cases considered to present the greatest risk of error, such as where a single fingerprint is identified, excluded, or deemed inconclusive

Segura reading

-American Academy of Forensic Science (AAFS) conference theme: -Celebrating the Forensic Science Family (2015) -Transformation: Embracing Change (2016) -After the AAFS meeting in 2015: -Abrupt halting of DNA testing in DC lab -Massachusetts chemist falsified thousands of drug tests over hernine-year career -Texas man was freed after 25 years in prison due to bite-mark evidence -Three men were exonerated in New York after more than 30 years based on faulty arson investigation -National Registry of Exonerations reported that 45% of cases involved false or misleading forensic evidence -FBI analysts doing hair examination gave flawed testimony in almost all trials in which they offered evidence against criminal defendants

Other Organizations in forensic science

-American Academy of Psychiatry and the Law -American Society of Crime Laboratory Directors -International Association for Identification -National Association of Medical Examiners -Society of Forensic Toxicologists and American Board of Forensic Toxicology

Single-source or simple-mixture samples - Computing DNA Statistics

-Each lab examines at least 12 or 16 or 24 loci (a fixed position) on the human genome where there are STRs (short tandem repeats) -If two DNA samples are from the same person, they will have the same alleles at each locus examined; if two samples are from different people, they will almost always have different alleles at some of the loci -even one dismatch = not person -if this is the same person we will expect in all of the locations we'll see the same alleles, it doest mean that theres only one person that will have the same ones (more than one person can be a possible match) -use random probability error to see how confident you can be with the match

A review of the FBI's handling of the Brandon Mayfield case

-An FBI examiner concluded with "100 percent certainty" that the fingerprint matched Brandon Mayfield, an American in Portland, Oregon, even though Spanish authorities were unable to confirm the identification -Reviewers believe the misidentification resulted in part from "confirmation bias" and "reverse-reasoning" that is, going from the known print to the latent image in a way that led to over reliance on apparent similarities and inadequate attention to differences -An appropriate analysis where features were identified in the latent before examining the control print -correctly concluded that the two prints were not from the same source -bad analysis: features annotated were generally selected only ofter examining the control print -erroneously concluded that the two prints were from the same source -The erroneous decision may have been influenced by bias, that is, the examiner may only have observed and annotated features that would support a preconceived conclusion of identification -FBI produced a 330-page report about where its analysts went wrong -Case study of many potential downfalls of fingerprint identification: -Ignoring differences between prints -Lack of independent verification -Pressure of working on a high-profile terrorism investigation -Letting bias about suspect affect their analysis

Who analyzes fingerprints?

-Analysis is performed in various settings including -Accredited crime laboratories and non-accredited facilities -Crime laboratories, police identification units, or private consultants -Sometimes analysts focus only on (latent) print examination, and sometimes they may perform other forensic casework -In some agencies -Fingerprint examiners are also required to respond to crime scenes -Can be sworn officers who also perform police officer/detective duties

The History of Fingerprint Identification

-Ancient carvings 3000 BC: people were aware of patterns on fingers, and there are carvings of patterns -William Hershel (1833-1917) was a British ICS officer in India who used fingerprints for identification on contracts -Is credited with being the first European to note the value of fingerprints for identification -He used them in India to control fraud in government contracts and pensions -Henry Faulds (1843-1930) was a Scottish doctor, missionary and scientist who is noted for the development of fingerprinting -Suggested using fingerprints in criminal investigations -Offered to set up a unit at Scotland Yard in 1886 and was rejected -Ivan Vucetich (1858-1925) was a Croatian-born Argentine anthropologist and police official -In 1892 Vucetich made the first positive identification of a criminal in a case where Francisca Rojas had killed her two children and then cut her throat, trying to put the blame on the outside attacker -A bloody print identified her as the killer -Argentine police adopted Vucetich's method of fingerprinting classification and it spread to police forces all over the world -Late 1800s: Bertillon's system of 11 body measurements was used to classify individuals -1892: Galton studied minutiae in fingerprints and wrote about the technique of identifying common patterns in fingerprints -Sir Edward Henry (1850-1931): was the Commissioner of Police of the Metropolis (head of the Metropolitan Police of London) -Developed a system of fingerprint classification enabling fingerprint records to be organized and searched with relative ease -The Scotland Yard adopted the "Henry" system -1904, St. Louis, MO: Scotland Yard instructs US police at World Fair -1905: US army starts using it -1911: First conviction based on fingerprint evidence in Illinois -1924: FBI identification division started

Massachusetts chemist falsified thousands of drug tests

-Annie Dookhan was employed as a chemist in the drug analysis unit of the Hinton State Lab in Jamaica Plain, near Boston, MA, which tested drug evidence submitted by law enforcement across the state -In June 2011, a problem was found with Dookhan's work: she had not written her name down for some samples she had analyzed, and she had written someone else's name down. This prompted the state police to review her work -Dookhan admitted she had "dry labbed" some samples: merely visually identifying samples instead of performing the required chemical test -Dookhan would combine multiple drug samples from different cases that appeared to be the same substance -She would perform chemical tests on a few of the samples to verify that the samples were in fact what she thought, and if they were positive would assume all the samples were positive without performing the tests -She sometimes would say she had tested a sample even when the sample was not physically in the same building -She had not contaminated the original substances, so the investigators were able to re-test them and see where she had made mistakes or forged evidence -Dookhan had testified as an expert witness in 14 different trials -She said she had a master's degree in chemistry from UMass, but she did not

Fingerprint Certainty in court

-At present, fingerprint examiners typically testify in the language of absolute certainty -Both the conceptual foundations and the professional norms of latent fingerprinting prohibit experts from testifying to identification unless they believe themselves certain that they have made a correct match -Experts therefore make only what they term 'positive' or 'absolute' identifications - essentially making the claim that they have matched the latent print to the one and only person in the entire world whose fingertip could have produced it -Given the general lack of validity testing for fingerprinting; the relative dearth of difficult proficiency tests; the lack of a statistically valid model of fingerprinting; and the lack of validated standards for declaring a match, such claims of absolute, certain confidence in identification are unjustified -Therefore, in order to pass scrutiny under Daubert, fingerprint identification experts should exhibit a greater degree of epistemological humility -Claims of 'absolute' and 'positive' identification should be replaced by more modest claims about the meaning and significance of a 'match.'

How to acquire images of latent prints?

-Black powder -Magnetic powder -Super glue fuming developer -Ninhydrin spray and heat on paper, silver nitrate physical developer -Scanner (inkless)

more history of forensics

-Early 20th century, professionalism of law enforcement led to the birth of forensics -1904: Scotland Yard (London police) introduces fingerprint matching to US law enforcement at the World's fair in St. Louis -1911: prosecutors in Illinois used fingerprint evidence to convict Thomas Jennings -Around 1910: Vollmer, first police chief of Berkeley, CA, invented the crime lab: a scientific laboratory, using primarily forensic science for the purpose of examining evidence from criminal cases -Vollmer also started a criminal justice program at Berkeley: this was the birth of criminal justice as an academic field

Logic of forensic examinations

-Examine two samples to identify similarities and differences -Assess similarities and differences to see if they are expected (or likely) under the same source hypothesis -Assess similarities and differences to see if they are expected (or likely) under the different source hypothesis

State admissibility standards - don't prevent bad science from entering the courts

-But neither standard has done much to keep bad science out of criminal trials -In the 1970s, the FBI looked at "voice printing": the idea that every human voice gives off distinctive patterns that make them uniquely identifiable and that these patterns can be measured and quantified -Critics began to raise questions about the science behind the methodology -The NAS group concluded that the methodology wasn't grounded in sound science -The FBI dropped voice printing, but not until it had already been admitted as evidence in dozens of courts across the country -Other examples include wrongful convictions based on arson, NAS refuted FBI theory about uniqueness of a batch of ammunition and more -The main reason that unproven but scientific-sounding claims get into court is that we're still asking judges to referee good science from bad, and judges just aren't very good at that -Saks suggests a sort of national forensics panel that would evaluate new and existing forensic specialties and decide which have sufficient scientific support to be allowed in the courtroom

The evaluation is based on two type of characteristics

-Class characteristics: Not unique to a particular object but place the particular bit of evidence into a group of objects -Individual characteristics: Assumed to narrow down the evidence to a single, individual source -The model of the shoe print left at a crime scene and The ABO typing of blood sample (i.e: AB negative) are class characteristics -The wear and the random marking on the shoe are individual characteristics -The likelihood of finding physical evidence with individual characteristics is smaller than the likelihood of finding class physical evidence -If the laboratory can piece broken glass from a window or headlight together, then the evidence has individual characteristics -Evidence having class characteristics can exonerate an innocent suspect -The value of class physical evidence lies in its ability to corroborate events with data in a manner nearly without bias

Analysis: The examiner considers information such as

-Condition of the skin (consequences of aging - wrinkles, damage, scars, masking attempts) -Type of residue - the substance from which the fingerprint was created: blood sebum (oily, waxy substance secreted by the Sebaceous glands in the skin) paint -Mechanics of touch (compression, stretching, rotation, uneven bone pressure -Nature of surface touched (texture, shape, condition) -Development technique (black powder, magnetic powder, super glue fuming etc) -Capture technique (photograph, lifting material) -Size of the print (percentage of surface that is available for comparison). If latent print does not have enough information, it does not undergo the rest of the process

What is DNA?

-DNA (deoxyribonucleic acid) is a molecule (a group of atoms bonded together) inside the nuclei of cells -Carries genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses -Human cells have 23 pairs of chromosomes -22 pairs of autosomes (any chromosome that is not a sex chromosome) -One pair of sex chromosomes -The DNA is the same in each of the cells in the body -DNA is composed of two chains (made of nucleotides) -Each nucleotide is composed of one of four nitrogen-containing nucleobases, cytosine [C], guanine [G], adenine [A] or thymine [T], a sugar called deoxyribose, and a phosphate group -The nucleotides are joined to one another in a chain by covalent bonds -The bases of the two strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double stranded DNA -Over 99% of DNA is identical among humans -A printed version of your entire genetic code would occupy some 262,000 pages, or 175 large books -Of those pages, just about 500 would be unique to each person -This is because large chunks of our genome perform similar functions across the animal kingdom -Value to forensic science: Variations in DNA sequence determine our individuality

State admissibility standards

-Daubert and Frye propose two different standards of admissibility in expert testimony -Frye evaluates the "general acceptance" of the testimony in the field from which it comes -Daubert tasks judges to evaluate the "methods and priniciples" upon which the expert opinions are founded -Many state courts have expressed that Daubert constitutes a more liberal standard for admissibility than Frye -On the flip side, some courts have found that Daubert in practice actually constitutes a more restrictive test -Frye looks at whether expert knowledge is "generally accepted" -Therefore, expert evidence that is generally accepted but has weak scientific foundation can be admitted -Daubert inspects the "methods and principles" underlying expert opinion -As a result, opinions that have strong scientific foundation, but have not been generally accepted, can be admitted -In many cases, the two are consistent. But in some cases (i.e. bitemark evidence), the two can diverge -North Dakota, North Carolina, and South Carolina are not on the Frye/Daubert continuum - they have their own standards for admissibility.

Abrupt halting of DNA testing in DC lab

-Director of the District's first independent DNA lab resigned after two audits found that the lab's procedures were inadequate, forcing a national accreditation body to suspect all of the lab's DNA testing -The analysts at the lab were "not competent" and were using "inadequate procedures." -The prosecutors said the errors have not resulted in the dismissal of any cases or in any exonerations -Prosecutors, as well as the accreditation board, had problems with the interpretation in DNA mixtures cases, those in which more than one person's DNA is present in the evidence -Houck has repeatedly defended the lab's operations, even after prosecutors said they found numerous flaws in the analyses. Houck argued that his lab technicians followed the same protocol that many city and state labs across the country use in interpreting evidence

reproducibility

-Do different examiners obtain the same measurement or reach the same conclusion when analyzing the same materials? -Repeatability is intra-examiner reliability, whereas reproducibility is inter-examiner reliability -Reproducibility is typically lower than repeatability because differences among examiners as well as differences in the performance of the same examiner come into play -Reproducibility can be measured by examining the correlations of different pairs of raters or through the calculation of the intraclass correlation coefficient, a summary statistic that estimates the correlation that would be expected between two different examiners -ex. In an earlier study of 169 examiners, each examiner assessed approximately 100 image pairs selected from a pool of image pairs -The inter-examiner agreement was slightly lower than the intra-examiner repeatability

The Association of Firearm and Toolmark Examiners (AFTE)

-International non-profit organization dedicated to the advancement of firearm and toolmark identification -Professional organization for practitioners of Firearm and/or Toolmark Identification and has been dedicated to the exchange of information, methods and best practices, and the furtherance of research since its creation in 1969

Steps for IAFIS search

-Examiner encodes latent print on computer screen by marking selected ridge deviations such as ending ridges and bifurcations -The IAFIS program compares the pattern of points in the latent print, as encoded by examiner, with the patterns of points in millions of known fingerprints in its databases -Examiner uses available information to narrow the scope of the databases that are searched (sex, race) -The IAFIS program generates a list of 10 or 20 candidates whose known fingerprints score the highest according to a complex algorithm that measures the correspondence of points in the known prints with the encoded points -The algorithm produces candidates, rankings and a "match score" -The numerical score generated by IAFIS is less significant than the gap between the top scoring candidate and the other candidates -Large gap: high probability that the top candidate is in fact the source of the print -IAFIS is designed to find not only the source of the print (if it is in the database), but also the closest possible non-matches -In other words, although no two people have identical fingerprints, there are some that may be sufficiently close to confuse an examiner dealing with a latent of imperfect clarity -Examiner then conducts a manual examination of the prints using ACE-V

What about the iPhone Touch ID technology?

-Fingerprint scanners at airports, iPhone, companies, etc -How do these work? -Touch ID: conductivity of valleys (as opposed to ridges) -Takes image, converts it to mapping, encrypts this, compares to database of mappings, and finds a match -Why not do this in law enforcement? -Can't get conductivity mapping from latent print

Calculation in more detail

-For locus D3S1358, for example, the allele frequencies are 0.103 and 0.262 (which means that 10.3 percent of the alleles observed for this locus are "14" and 26.2 percent are "15") -So the frequency of the pair of alleles (genotype) is 0.103 x 0.262 x 2 = 0.054 -Which means that among U.S. Caucasians approximately 1 person in 18.5 would have this genotype -If there is only one allele at a locus (inherited the same allele from both parents), then the frequency is simply p^2, where p is the frequency of that allele -The frequencies of the genotypes at each locus are then all multiplied together to produce a frequency estimate for the overall profile -The overall frequency is approximately 0.0002177, which means that approximately one person in 4,592 would be expected to have this particular three-locus profile

What is forensics?

-Forensic (or forensis, in Latin) means a public discussion or debate -In a modern context, forensic applies to courts or the judicial system -Forensic Science - the application of scientific methods and processes to solve crimes -Forensic science now ranked 2nd factor associated with wrongful conviction

Is fingerprint identification foundational valid? PCAST conclusions

-Foundational validity: Based largely on two recent appropriately designed black-box studies, PCAST finds that latent fingerprint analysis is a foundationally valid subjective methodology - albeit with a false positive rate that is substantial and is likely to be higher than expected by many jurors based on longstanding claims about the infallibility of fingerprint analysis -Conclusions of a proposed identification may be scientifically valid, provided that they are accompanied by accurate information about limitations on the reliability of the conclusion. specifically, that: 1) Only two properly designed studies of the foundational validity and accuracy of latent fingerprint analysis have been conducted 2) These studies found false positive rates that could be as high as 1 error in 306 cases in one study and 1 error in 18 cases in the other 3) Because the examiners were aware they were being tested, the actual false positive rate in casework may be higher -At present, claims of higher accuracy are not warranted or scientifically justified -Additional black-box studies are needed to clarify the reliability of the method -Validity as applied: Although we conclude that the method is foundationally valid, there are a number of important issues related to its validity as applied 1) Confirmation bias: -Work by FBI scientists has shown that examiners typically alter the features that they initially mark in a latent print based on comparison with an apparently matching exemplar -Such circular reasoning introduces a serious risk of confirmation bias -Examiners should be required to complete and document their analysis of a latent fingerprint before looking at any known fingerprint and should separately document any additional data used during their comparison and evaluation 2) Contextual bias: -Work by academic scholars has shown that examiners' judgments can be influenced by irrelevant information about the facts of a case -Efforts should be made to ensure that examiners are not exposed to potentially biasing information 3) Proficiency testing: -Proficiency testing is essential for assessing an examiner's capability and performance in making accurate judgments -As discussed elsewhere in this report, proficiency testing needs to be improved by making it more rigorous, by incorporating it within the flow of casework, and by disclosing tests for evaluation by the scientific community From a scientific standpoint, validity as applied requires that an expert: 1) Has undergone appropriate proficiency testing to ensure that they are capable of analyzing the full range of latent fingerprints encountered in casework and reports the results of the proficiency testing 2) Discloses whether he or she documented the features in the latent print in writing before comparing it to the known print 3) Provides a written analysis explaining the selection and comparison of the features 4) Discloses whether, when performing the examination,they were aware of any other facts of the case that might influence the conclusion 5) Verifies that the latent print in the case at hand is similar in quality to the range of latent prints considered in the foundational studies

1892: Sir Francis Galton, inspired by the work of Alphonse Bertillon, writes about how useful fingerprints are for identifying individuals

-Francis Galton coined the term "eugenics." -The science of improving a human population by controlled breeding to increase the occurrence of desirable heritable characteristics -Became unpopular only after the perversion of its doctrines by the Nazis -Believed that certain physical traits (nose size, skull shape or skin tone) are indicative and predictive of criminality, intelligence, virtue, morality, and others -Advocated for the forced sterilization of entire groups of people -Considered the father of the modern fingerprint -1892-1895: inspired by Bertillon wrote three books -Estimated the probability that two finger prints which are alike in their minutiae were made by different persons -Studied how unique fingerprints are and the heritability and racial differences in fingerprints -He wrote about techniques for identifying common fingerprint patters and devised a classification system that survived to this day

Frye v. United States (1923): In order to be admissible in federal court, scientific evidence or testimony must have "gained general acceptance in the particular field in which it belongs."

-Frye was soon adopted by other federal circuits and eventually by most of the states (it wasn't a Supreme Court decision) -"Frye looked beyond a witness' qualifications to evaluate the content of the witness' testimony" -It made judges the gatekeepers of scientific evidence

Forensic DNA

-In the mid-1980s, the first DNA profiling techniques were developed -The name DNA 'fingerprinting' was widely used -At the time, fingerprinting was a well-established forensic method, and it was rarely questioned in the courts -Fingerprint examiners were permitted to describe matching prints as evidence of individual identity -DNA 'fingerprinting' went through a period of controversy, especially in the US courts -By the late 1990s DNA profiling was so widely accepted that it became a basis for invidious comparison with all other forms of forensic evidence, including fingerprinting -DNA is obtained from blood, saliva, semen, hair, urine, teeth, bones and various tissues

The uniqueness fallacy

-Galton noted: -Extreme variability among individuals -Persistence of the friction ridge patterns within an individual over several decades -Later studies indeed showed that apart from significant injuries or illnesses that can scar the dermis, the friction ridge pattern does not change throughout at person's life -Galton's findings of variability among individuals neither demonstrated uniqueness, nor was intended to do so -In fact, it is not possible to demonstrate that fingerprints are unique. Formally, one would need to compare all possible pairs of individuals to make that claim -Crime scene fingermarks are often, even usually partial, distorted, and potentially degraded representations of the friction skin and only display an extremely limited amount of discriminating information -The uniqueness fallacy lies in the use of the claim that the friction ridge pattern on the skin of the finger is unique to justify the association of a low-quality mark to a unique source -In other words, while a constellation of 70 high-quality minutiae on the skin of a finger might not be duplicated on any other finger, many fingers might show sets of six minutiae that could be associated with a set of six minutiae observed on a partial and distorted mark.

Galtons goal and procedure on fingerprints

-Galton's goal was to answer the following question: Given two fingerprints which are alike in their minutiae, what is the chance that they were made by different persons? -He wanted to get an approximate numerical value of fingerprints as a means for personal identification -The general procedure: Given two fingerprints, perform a general examination of their patterns -If they do not agree in being arches loops or whorls, then there is "no doubt" that they come from different fingers -Otherwise, there is "no doubt" that they belong to the same general class -Most patterns are not easily distinguishable from one another -Calculated the chance of exact correspondence between two different fingerprints -According to Galton, The probability of two specific fingerprints being the same is around 1 in 6,400,000,000 -Possible problems: His calculations relayed on a subjective process (It sounded very "scientific.")

Foundational validity of ACE-V in NAS 2009

-Haber and Haber (2007) present a thorough analysis of the ACE-V method and its scientific validity -Their conclusion is unambiguous: "We have reviewed available scientific evidence of the validity of the ACE-V method and found none." -Clearly, the reliability of the ACE-V process could be improved if specific measurement criteria were defined -Those criteria become increasingly important when working with latent prints that are smudged and incomplete, or when comparing impressions from two individuals whose prints are unusually similar

(History) Mid 1800s: Alphonse Bertillon invents system to identify individuals based on body measurements

-His father arranged for his employment in a low-level clerical position with the police -As a Paris police officer he pioneered the use of anthropometry - taking and recording careful measurements of body parts for the purpose of identification -Bertillon's methodology helped law enforcement identify repeat offenders (important because recidivism had been rising since 1870, and fingerprints were not being used for identification at that time) -By the end of the 19th century, Bertillon's system had been adopted by police agencies across the U.S. and Europe -It was one of the first examples of scientific classification in law enforcement -Later,Poincare, Darboux, and Appell, concluded that Bertillon's system was deprived of any scientific value and that he had failed both to apply the method and to present his data properly -Developed forensic techniques, such as compounds to preserve footprints -1888: Invented the mug shot (standardized process of photographing criminals in front and side) -1894, 1899: Bertillon testified as a handwriting expert against Alfred Dreyfus, an officer in the army (most notable example of a complex miscarriage of justice and antisemitism) -1912: Publication of Bertillon article stating that 16 ridge characteristics are sufficient to identify latent prints at crime scene

Threshold for a "match"

-If an individual's DNA profile matches in all 12 to 24 areas (depending on the lab) to a DNA profile developed from evidence in a crime scene, then this is considered a "match" -this means whats the probability that some random person would match THIS profile, its not based on a comparison

Goal of forensic DNA testing

-In biological science research, DNA testing has mostly been used to study evolution and the origins of species -In forensic science, the goal of forensic DNA testing is to determine whether two biological (from crime scene and suspect) samples came from the same source -It was first used in paternity tests and later in identification

Comparison

-In the Comparison phase, the examiner compares the latent print to one or more exemplar prints -Information gathered in the earlier analysis of the latent print provides a starting point -A criticism of the latent print community is that the examiners can too easily explain a "difference" as an "acceptable distortion" in order to make an identification -A comparison of L1D might take only a split second, as when a whorl is present in the latent, but an arch is apparent in the exemplar -If there is no exclusion based upon L1D, then the examiner continues the comparison -If the examiner finds disagreement with respect to the exemplar that is too extensive to be the result of the distortion noted in the Analysis phase, the examiner will exclude the source of the exemplar as the source of the latent -If the examiner locates a comparable set of L1D features in the known exemplar, the examiner proceeds to a detailed, side-by-side comparison of L2D and possibly L3D -If the examiner concludes that the extent of agreement between the two prints satisfies his or her threshold, then the examiner proceeds to the Evaluation phase

Automated fingerprint identification systems

-In the late 1970s and early 1980s, law enforcement agencies across the Nation began adopting Automated Fingerprint Identification Systems (AFIS) to improve their efficiency and reduce the amount of time it took to -Identify (or not exclude) a given individual from a fingerprint -Conduct a background investigation -Before the use of AFIS, the fingerprint identification process involved numerous clerks and fingerprint examiners sifting through thousands of tediously classified and cataloged paper fingerprint cards, while dealing with delays and challenges caused by the realities of exchanging information with other agencies by mail, fax, or other means -AFIS is managed primarily by uploading 10-print records from police bookings and background checks -Submitting a latent print for comparison is a more customized process, requiring fingerprint examiners to mark or adjust the features manually to retrieve stored prints with the same features in analogous places -Algorithms are not as good (yet) as the human eye in spotting features in poor images

The National Registry of Exonerations

-Internationally recognized repository of information and research on exonerations of innocent defendants convicted of crimes in the U.S -These are the cases in which a person was wrongly convicted of a crime and later cleared of all the charges based on new evidence -A joint project of the UCI Newkirk Center for Science & Society, University of Michigan Law School and Michigan State University College of Law -Founded in 2012 in conjunction with the Center on Wrongful Convictions at Northwestern University School of Law -The registry, which relies entirely on public information, collects, analyzes and disseminates detailed data on every known exoneration since 1989

American Academy of Forensic Sciences (AAFS)

-Is a society for forensics professionals, founded in 1948. Based in Colorado Springs, Colorado, USA -Is a multi-disciplinary professional organization that provides leadership to advance science and its application to the legal system -Consists of different sections in the branches of Anthropology, Criminalistics, Digital & Multimedia Sciences, General, Engineering Sciences, Jurisprudence, Odontology, Pathology/Biology, Psychiatry & Behavioral Science, Questioned Documents, and Toxicology -The Journal of Forensic Sciences is published by Wiley-Blackwell on the Academy's behalf Forensic Science, Law, and Society C132 N

The Center for Statistics and Applications in Forensic Evidence (CSAFE)

-Is the National Institute of Standards and Technology (NIST) center of excellence -An interdisciplinary team of researchers from five universities: (Iowa State University, Carnegie Mellon University, University of California Irvine, University of Virginia, Duke University) -The CSAFE team works to build a statistically sound and scientifically solid foundation for the analysis and interpretation of forensic evidence to grow competence in the forensic sciences and legal communities, and bring together forensic practitioners and other stakeholders through educational and training opportunities

Galton on fingerprints

-It is the first attempt to place the study of fingerprints on a scientific basis and so lay the groundwork for their use in criminal cases -He was able to collect a large sample of prints through his anthropological laboratories, eventually amassing over 8,000 sets -His study of minutiae in prints provided the foundation for a meaningful comparison of different prints -Galton also provided the first workable fingerprint classification system, which was later adapted by E. R. Henry for practical use in police forces and other bureaucratic settings -Most of all, Galton's extensive popular advocacy of the use of prints helped to convince a skeptical public that they could be used reliably for identification -Galton also published a great number of scholarly papers, popular articles, letters and interviews on the subject of fingerprints

1993: Daubert cases

-Judges must consider two criteria: the relevance of expert testimony and its reliability -Under Daubert, an opposing attorney can request a hearing in which the judge will rule on the admissibility of scientific evidence. -Daubert standard defined the term "scientific methodology" and established a list of criteria for the admissibility of scientific expert testimony: -Whether the theory or technique employed by the expert is generally accepted in the scientific community; -Whether it has been subjected to peer review and publication; -Whether it can be and has been tested; -Whether the known or potential rate of error is acceptable; -Whether the research was conducted independent of the particular litigation or dependent on an intention to provide the proposed testimony.

To determine the print's value, the examiner considers three levels of detail in the impression:

-Level 1 Detail (L1D) is defined as "ridge flow." -Ridge flow often translates to a pattern type in a finger or palm, such as a loop, whorl, or arch formation -Pattern types are class characteristics shared by many individuals -Ridge flow also includes other information such as relative curvature -Level 2 Detail (L2D) is defined as "ridge path." -L2D includes, but is not limited to, minutiae, such as ridge endings, bifurcations, or dots -Even the absence of minutiae in an area (called an "open field") can be significant and highly discriminating -Level 3 Detail (L3D) is defined as "ridge shapes." -Ridge shapes include the edges of ridges (which may appear indented or protruded) -Pores (the location of the center of the pore, not the size or shape, which can be highly variable within a source)

Early 20th century: Dr Edmond Locard formulated the basic principle of forensic science as: "Every contact leaves a trace"

-Locard's exchange principle holds that the perpetrator of a crime will bring something into the crime scene and leave with something from it, and that both can be used as forensic evidence -French criminalist known for being a pioneer in forensic science and criminology "Sherlock Holmes of France" -Published over 40 pieces of research, the most famous being his seven-volume series Traite de criminalistique (Treaty of Criminalistics) -Locard worked with the French Secret Service as a medical examiner

Validity as applied

-Means that the method has been reliably applied in practice -It is the scientific concept we mean to correspond to the legal requirement, in Rule 702(d) that an expert "has reliably applied the principles and methods to the facts of the case." -Refers to whether the examiner correctly applied the method (whether predominantly subjective or objective) in a particular case -PCAST suggests that this requirement for admissibility can be established through information about the performance of the examiner on rigorous proficiency tests and through careful documentation and review of the analysis performed in the case -When such information does not demonstrate that the analyst followed the validated procedure, courts should exclude the finding -In a recent case in North Carolina (State v. McPhaul), a latent fingerprint examiner could say only that "I did comparisons - side-by-side comparisons." -She did not specify what features of the prints she compared or even how long the examination took -The state court of appeals held that the examiner "failed to demonstrate that she 'applied the principles and methods reliably to the facts of the case,' as required by Rule 702(a)(3)"

Minutiae and Database search

-Minutiae: Events along a ridge path, including bifurcations (points at which one friction ridge divides into two friction ridges), dots (isolated friction ridge units that have lengths similar their widths), and ridge endings (the abrupt end of ridges) -Database search: Examiner might compare two prints, or search a large database of prints to identify a suspect

The Innocence Project

-Non-profit legal organization committed to exonerating wrongly convicted individuals through the use of DNA testing (and other techniques) and to reforming the criminal justice system to prevent future injustice -Was founded in 1992 by Barry Scheck and Peter Neufeld

National Institute of Standards and Technology (NIST)

-Non-regulatory agency of the United States Department of Commerce -Its mission is to promote innovation and industrial competitiveness -NIST's activities are organized into laboratory programs that include nanoscale science and technology, engineering, information technology, neutron research, material measurement, and physical measurement -Started in 1901, in response to a bill proposed by Congressman James H. Southard (R, Ohio), the National Bureau of Standards was founded with the mandate to provide standard weights and measures, and to serve as the national physical laboratory for the United States -Due to a changing mission, the "National Bureau of Standards" became the "National Institute of Standards and Technology" in 1988 -NIST includes Forensic Science Standards Board and OSAC (will be explained below)

ACE-V problems

-Note that the ACE-V method does not specify particular measurements or a standard test protocol, and examiners must make subjective assessments throughout -Thresholds based on counting the number of features that correspond, lauded by some as being more "objective," are still based on primarily subjective criteria - an examiner must have the visual expertise to discern the features (most important in low-clarity prints) and must determine that they are indeed in agreement -In the United States, the threshold for making a source identification is deliberately kept subjective, so that the examiner can take into account both the quantity and quality of comparable details -As a result, the outcome of a friction ridge analysis is not necessarily repeatable from examiner to examiner -In fact, recent research by Dror has shown that experienced examiners do not necessarily agree with even their own past conclusions when the examination is presented in a different context some time later (more on this when we talk about cognitive bias)

Electropherogram

-Plot of DNA sequencing results -Here 16 loci (a fixed position) are examined (now labs are moving to using 23) -more loci's used the more unique it will be -Different nucleotide sequences have different pigment color codes -The upper right "AMEL" label is the gender chromosome -Female: XX, Male XY -The label D3S1358 indicates that it is chromosome 3 and the name of the loci (its specific place in the loci) is S1358 -this is called nomenclature -The hight of the peaks correspond to relative fluorescence units (RFU) - which relates to the amount of DNA -The numbers under the peaks on the X-axis indicate the number of repeats at each loci (alleles) -Heterozygous: having two different alleles and therefore two peaks (e.g at D3S1358, 17,18) -Homozygous: having two identical alleles and therefore one peak (e.g at D22S1045, 16,16) -When there is a single-source DNA, the two peaks (in the heterozygous case) in each chromosome are expected to have the same height -The peak is expected to have double the hight in the homozygous case

Exemplar or known prints

-Prints deliberately collected from an individual -Exemplar prints can be collected electronically or by using ink on paper cards -Exemplars may be called ten-prints when impressions of all ten fingers are taken -Exemplar prints collected during criminal arrests normally include one rolled (from one side of the nail to the other) print of each finger pad and a plain or slap impression of each finger

repeatability

-Refers to the reliability of measurements or conclusions by a particular examiner under the same conditions -Does the same examiner give the same answer using the same instrumentation or approach if provided with the same materials a second time? -ex. In a fingerprint analysis, 72 latent fingerprint examiners repeated analyses of pairs of prints with known truth (i.e., mated pairs or non-mated pairs) seven months after the examiners first analyzed the pairs -For the true mates, repeatability of decisions (including "inconclusives") was 90% ; For the pairs of non-mates, repeatability was 86% -As one would expect, when the latent print in the pair was blurry or incomplete, repeatability was lower than when the print was clear and more complete -Repeatability is likely to vary from one forensic discipline to another and depends on the particular task -Unfortunately, there are few studies of repeatability with high-quality experimental designs

what is a fingerprint?

-Ridges in upper layer of skin (epidermis), sometimes called "friction ridges" -Ridges contain pores for secretion of perspiration -Developed in fetus at 17 weeks -Theory: Provide friction for grasping -Parts: Core (center), type lines (lines surrounding the center), delta (triangular area where lines meet) -Fingerprints are deposited on suitable surfaces (such as glass or metal or polished stone) by the natural secretions of sweat from the eccrine glands that are present in epidermal ridges

Evaluation

-Source determination is made when the examiner concludes, based on their experience, that sufficient quantity and quality of friction ridge detail is in agreement between the latent print and the known print. -Source exclusion is made when the process indicates sufficient disagreement between the latent print and known print. -If neither an identification nor an exclusion can be reached, the result of the comparison is inconclusive. -Options: Individualization (or identification), exclusion, or inconclusive -The thresholds for these decisions can vary among examiners -Some examiners state that they report identification if they find a particular number of relatively rare concurring features, for instance, eight or twelve -Others do not use any fixed numerical standard -Some examiners discount seemingly different details as long as there are enough similarities between the two prints -Other examiners practice the one-dissimilarity rule, excluding a print if a single dissimilarity not attributable to perceptible distortion exists -If the examiner decides that the degree of similarity falls short of satisfying the standard, the examiner can report an inconclusive outcome -If the conclusion is that the degree of similarity satisfies the standard, the examiner reports an identification

science in the law

-Special role of the expert witness -Special impact on the jury -This is why we have "gatekeeping"

Texas man was freed after 25 years in prison due to bite-mark evidence

-Steven Mark Chaney was sentenced to life in prison in 1989 for the murder of his wife Sally -Nine witnesses said they saw him elsewhere -A forensic dentist told jurors it was his teeth that caused bite-marks on the arm of a dead drug dealer named John Sweek: "One in a million chance that the marks could have come from anyone else." -On October 2015, after sending more than a quarter of a century in prison, he's been freed by a Texas state court judge, thanks to new reports saying that bite-mark analysis has little "scientific basis." -Chaney isn't necessarily innocent, but the evidence that he was guilty was deeply flawed according to lawyers, advocates and the Dallas County District Attorney

Three men were exonerated in New York after more than 30 years based on faulty arson investigation

-The 34-year-old case against the trio fell apart when prosecutors learned that Hannah Quick, the owner of the building that burned, gave numerous contradictory statements, including about how the fire started -Quick was a convicted felon and police informant who sold drugs out of the building where the fire occurred -Before dying, she confessed to family members she'd lied to investigators -Prosecutors also learned the fire marshal who initially investigated the case relied on antiquated notions of how fires start

IAFIS (the FBI's AFIS)

-The FBI's IAFIS is a system for conducting computerized searches of FBI databases containing the known fingerprints of over 47 million individuals (over 470 million separate prints) -The LPU (Latent Print Unit) examiners use IAFIS in attempt to identify latent fingerprints in cases lacking known subjects -Whose fingerprints are in the database? -The IAFIS databases include a Criminal Master File containing known prints taken pursuant to local, state, and federal arrests -A Civil File containing known prints taken in a non-criminal context, such as for military service or government employment -A Special Latent Cognizant File containing the known fingerprints of terrorism suspects and victims -An unsolved Latent File containing unidentified latent fingerprints from unsolved crimes

2009 National Academies Report

-The National Research Council of the National Academies of Science wrote landmark report: Strengthening Forensic Science in the United States: A Path Forward -Urged the U.S. government to establish an "independent federal entity" to address deep and widespread problems with the state of forensics -The study was a wake-up call to the scientific and legal communities, raising major concerns over the way analysts handle the most common and longstanding forms of forensic evidence -"With the exception of nuclear DNA analysis," the NAS report read, "no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source."

Organization of Scientific Area Committees for Forensic Science (OSAC)

-The Organization of Scientific Area Committees (OSAC) for Forensic Science works to strengthen the nation's use of forensic science by: -Facilitating the development of technically sound forensic science standards -Promoting the adoption of those standards by the forensic science community -These standards are -Written documents that define minimum requirements -Best practices -Standard protocols -Other guidance to help ensure that the results of forensic analysis are reliable and reproducible -OSAC is administered by the National Institute of Standards and Technology (NIST), but the great majority of its more than 550 members are from other government agencies, academic institutions, and the private sector -These members have expertise in twenty five specific forensic disciplines, as well as general expertise in scientific research, measurement science, statistics, law, and policy -OSAC members work together to develop and evaluate forensic science standards via a transparent, consensus-based process that allows for participation and comment by all stakeholders

2016 PCAST Report

-The President's Council of Advisors on Science and Technology (PCAST) released its latest report to the President, Forensic Science in Criminal Courts: Ensuring Scientific Validity of Feature-Comparison Methods -"Forensic science" refers to the application of scientific or technical practices to the recognition, collection, analysis, and interpretation of evidence for criminal and civil law or regulatory issues PCAST concluded that two important gaps warranted the group's attention: 1) The need for clarity about the scientific standards for the validity and reliability of forensic methods 2) The need to evaluate specific forensic methods to determine whether they have been scientifically established to be valid and reliable -The study aimed to help close these gaps for a number of forensic "feature-comparison" methods -recommendations: -NIST should perform evaluations, on an ongoing basis, of the scientific validity of current and newly developed forensic feature-matching technologies and should issue an annual public report on the results -NIST should take a leadership role in transforming three important feature-comparison methods - DNA analysis of complex mixtures, latent - fingerprint analysis, and firearms analysis - from currently subjective methods, with their heavy reliance on human judgement, into objective methods, in which standardized, quantifiable processes require little or no judgment -The FBI Laboratory should undertake a vigorous research program to improve forensic science -The Attorney General should direct attorneys appearing on behalf of the Department of Justice (DOJ) to ensure that expert testimony in court about forensic feature-comparison methods meets the standards of scientific validity -The Attorney General should revise and reissue for public comment the DOJ proposed "Uniform Language for Testimony and Reports" and supporting documents to bring them into alignment with standards for scientific validity -When deciding the admissibility of expert testimony, Federal judges should take into account the appropriate scientific criteria for assessing scientific validity -PCAST focuses on validity of pattern matching disciplines -Defines foundational validity and validity as applied

Are exclusions easier?

-The determination of an exclusion can be straightforward if the examiner finds detail in the latent print that does not match the corresponding part of the known print, although distortions or poor image quality can complicate this determination -But the criteria for identification are much harder to define. They depend: -On an examiner's ability to discern patterns (possibly complex) among myriad features -On the examiner's experience judging the discriminatory value in those patterns

FBI studies 2011: Results

-The empirically estimated false positive rates are much higher than the general public (and, by extension, most jurors) would likely believe based on longstanding claims about the accuracy of fingerprint analysis -Overall, it would be appropriate to inform jurors that -Only two properly designed studies of the accuracy of latent fingerprint analysis have been conducted -These studies found false positive rates that could be as high as 1 in 306 in one study and 1 in 18 in the other study -This would appropriately inform jurors that errors occur at detectable frequencies, allowing them to weigh the probative value of the evidence -We also note it is conceivable that the false-positive rate in real casework could be higher than that observed in the experimental studies, due to exposure to potentially biasing information in the course of casework -Introducing test samples blindly into the flow of casework could provide valuable insight about the actual error rates in casework

Profile frequencies

-The frequency of each possible allele in different locus is calculated in the relevant population (based on samples) -you define the relevant population, its not done in lab already -The examiner uses the frequency of each of the matching alleles -The probability calculations are based on these frequencies -first multiply both allele frequencies from each loci which = genotype frequency -heterozygote = 2 x p x q ; homozygote = p x p -have to multiple hetero by 2 because theres two options (each allele could be from either mom or dad) -then you multiply each loci's genotype frequencies by each other which gives you the overall profile frequency (RMP) -to turn decimal into "1 in __" = 1/"decimal"

The forensic examination

-There are a range of questions that arise in forensic examinations - source conclusions, timing of events, cause/effect -Our focus is on source conclusions -Evidence (E) are items/objects found at crime scene and on suspect (or measurements of items) -occasionally write Ec (crime scene), Es (suspect) -may be other information available, (I) -Two hypotheses -Hs: "Same source" proposition (two samples have the same source) -Hd: "Different source" proposition (two samples have different sources) -Goal: assessment of evidence -Do items appear to have a common source -How unusual is it to find observed evidence/observed agreement by chance

How good is this "match"?

-To know how much weight to assign to such a "match," labs typically compute the random match probability (RMP) -RMP is the answer to a very specific question: What is the probability that a randomly chosen person from the reference population would happen to have the same DNA profile found in an evidence sample? -there may be another match too so whats the weight to this random match

Training to be a fingerprint (latent print) examiner

-Training varies from agency to agency. Agencies may -Have a formalized training program -Use an informal mentoring process -Send new examiners to a one to two week course -Two manuals: -The International Association for Identification (IAI) offers a training publication, "Friction Ridge Skin Identification Training Manual," -The Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST) offers a guideline, "Training to Competency for Latent Print Examiners." -Not all agencies require latent print examiners to achieve and maintain certification

Latent print

-Unintentional reproduction of the arrangement of ridges on the skin on the underside of the hands made by the transfer of materials from the skin to a surface -Latent (not yet developed) comes from the fact that the print must be made visible

Verification

-Verification in some agencies is a review of an examiner's conclusions with knowledge of those conclusions -In other agencies, it is an independent re-examination by a second examiner who does not know the outcome of the first examination -Verification procedures vary among forensic service providers -At one extreme, the verifier, presented with the first examiner's work, assesses the original conclusion -At the other extreme, the verifier, blinded to the initial examination, performs an independent examination

Field in crisis

-Wrongful convictions -Role of DNA -Serves as role model for better forensic science -Forces change in forensic science by making other disciplines look bad -Also has problems -Lack of science -Little science behind trace evidence (Fingerprints, Footprints and others) -Use of unscientific techniques and junk-science -Prosecutorial Culture -90% of accredited crime laboratories located in law enforcement agencies (Chicago Tribune) -Part of prosecution team -Allegiance to state rather than to truth -saw their role as members of the state's attorney's team. "They thought they were prosecution witnesses," he said. "They didn't understand they were just scientists." -Exaggeration of value of evidence "100% certain" -Failure to disclose exculpatory evidence -Laboratory Problems -Many labs remain unaccredited -Accreditation is done by peers -Lax judicial "gatekeeping" -Forensic evidence is not held to a high standard -Decisions about the validity of science are made by people who don't necessarily know much about it -Forensic evidence is nearly always offered by the prosecution

false positive vs false negative

-false positive: saying something is there (match) when there wasnt -sending someone to jail when they didn't commit crime -false negative: saying something isn't there (no match) when there was -sending someone free when they actually committed a crime -rather have less false positives than false negatives -error rate: false positive/negative divided by reality

Early 20th century continues with U.S. courts facing the challenge of how to distinguish expertise from artifice

-the professionalism movement promotes a more analytical approach to fighting crime -The rush to embrace new theories and new technologies also opened the door to charlatans, hucksters and frauds -"The standard at the time was that if someone had specialized knowledge, and that knowledge seemed to be helpful to investigators, then the court would allow the testimony...The problem was that there was no attempt to check the validity of what these witnesses were actually claiming."

Steps to generate a DNA profile

1) DNA is first chemically extracted from a sample containing biological material, such as blood, semen, hair, or skin cells 2) A predetermined set of DNA segments ("loci") containing small repeated sequences are amplified using the Polymerase Chain Reaction (PCR) -An enzymatic process that replicates a targeted DNA segment over and over to yield millions of copies -It also tags nucleotides with fluorescent molecules 3) After amplification, the lengths of the resulting DNA fragments are measured using a technique called capillary electrophoresis (which is based on the fact that longer fragments move more slowly than shorter fragments through a polymer solution) 4) The raw data collected from this process are analyzed by a software program to produce a graphical image (an electropherogram)

Federal Rules of Evidence 702

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if: -The expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; -The testimony is based on sufficient facts or data; -The testimony is the product of reliable principles and methods; and -The expert has reliably applied the principles and methods to the facts of the case

10-print vs. latent searches

AFIS searches today fall into two distinct categories: -10-print searches, which typically involve comparing relatively highquality, professionally obtained fingerprint images -For example, prints taken during an arrest or booking or as part of a background check - with fingerprint records in an agency database, such as the FBI's IAFIS or a state's criminal fingerprint database -Latent print searches, which are considerably more complicated than 10-print searches -A fingerprint examiner attempts to identify an individual by comparing a latent fingerprint from a crime scene with the records contained in an AFIS database -Latent prints are regularly of poor quality and may be only a partial print, and often fingerprint examiners do not even know from which finger a given latent print came from

Forensics vs academic science

Academic Science: -Replication of results -General laws of nature Forensic Science: -Not replicable -Specific facts of individual case -Litigation driven; used almost exclusively in court

Ideal AFIS according to NAS 2009

An ideal, comprehensive AFIS, for example, would be capable of automated: -Reading of latent prints -Encoding of most features of usable quality, including those features identified as Level 1 (fingerprint classes such as whorl, arch), Level 2 (minutiae), Level 3 (pores, cuts), and ridge paths, together with a provision for including other features that could be defined by the vendor/user -recognizing absent, blurred, double/multioverlap, poor-quality sections of an observed print and encoding the system to downweight, or omit entirely, during the search process -Recognizing any orientation information -Conducting database searches -Providing "best matches" -Collecting statistical data based on the quality of the print and numbers/types of features

A DNA profile

Analogy: -We receive two sets of encyclopedias including 23 books each (chromosomes) -One set is inherited from the mother and one from the father -Chosen paragraphs (loci) are examined, known to have significant variability across humans -The sequences of letters (STRs-short tandem repeats) are counted in the chosen paragraphs, in both versions of the books (alleles) -alleles are the number of repeats -It is possible that the lengths of the STRs in the two alleles are the same or different -This DNA profile is used for comparison

Evidence types

Biological evidence (blood type, DNA), latent prints, shoe prints/tire tracks, glass fragments, fibers, handwriting and others

What databases does an AFIS search through?

Databases: -They are stand-alone systems or part of relatively limited regional networks with shared databases or information-sharing agreements -Many law enforcement agencies also access the Integrated Automated Fingerprint Identification System (IAFIS - the FBI's AFIS) database

foundational validity

Foundational validity -For a forensic-science method requires that it be shown, based on empirical studies, to be repeatable, reproducible, and accurate, at levels that have been measured and are appropriate to the intended application -Foundational validity, then, means that a method can, in principle, be reliable. -It is the scientific concept we mean to correspond to the legal requirement, in Rule 702(c) of "reliable principles and methods." -For methods that classify samples as coming from the same or different sources, "foundational validity" means that examiners can "in principle" accurately assess whether a sample of questioned origin and one of known origin come from the same source -This quality must be established empirically, through tests that show that the identification procedure is "repeatable, reproducible, and accurate, at levels that have been measured and are appropriate to the intended application" -In the case of largely subjective judgements, such as those for bite-marks, toolmarks, and fingerprints validity can be established through studies in which "the method [is] evaluated as if it were a 'black box' in the examiner's head" -'Black box' studies treat examiners as decision-making "black boxes" and use examples with known ground truth to evaluate performance -Lacking a deep understanding of the process, researchers simply compare examiners' classifications of matched and non-matched pairs to the right answers -If the subjective classification process is valid, then both false-positive and false-negative errors will be rare in multiple studies with pairs that are representative of casework -PCAST found that recent publications on fingerprints established foundational validity for comparing latent fingerprints to exemplars -The false-negative rate was 50 times higher, with 7.5% of mated pair analyses excluding the source of the known print as the source of the questioned print -Indeed, 85% of the participating examiners made at least one false exclusion

How to and not to interpret RMP

How to interpret RMP: -The DNA test places a matching suspect, like Suspect 3, in a category of individuals who might have been the donor of this sample -The profile frequency (RMP) tells us something about the size of this group -In our example, it includes 1 in 4,592 Caucasians, which is a lot of people given that more than 100 million Caucasians live in the United States How not to interpret RMP: -The profile frequency does not tell us the probability that Suspect 3 was (or was not) the source of the blood at the crime scene -The DNA evidence cannot tell us whether Suspect 3 was more or less likely to be the donor than any of the other people who would also match -But it does tell us how broad a net was cast by the test - it was broad enough to incriminate about one person in 4,592, just by chance

science and law

Law relies on imperfect evidence: -Witnesses -Eye and character -Imperfect recollection -Untruthful -Experts -Doctors, others -Conflicting testimony -Law hoped science would produce clear truth -Science should function as an independent check on other, less trustworthy aspects of the justice system (witnesses, police, prosecutors, judges, juries, etc.)

What is "valid enough"?

PCAST does not tell us what is valid enough. Recall: -Foundational validity for a forensic-science method requires that it be shown, based on empirical studies, to be repeatable, reproducible, and accurate, at levels that have been measured and are appropriate to the intended application -Up to the trier of fact (i.e., judge or jury) to decide? Or a consensus of the discipline? Not stated

Is fingerprint identification foundational valid? PCAST

PCAST on fingerprints -Much credit goes to the FBI Laboratory, which has led the way in performing both black-box studies, designed to measure reliability, and "white-box studies," designed to understand the factors that affect examiners' decisions -There are also nascent efforts to begin to move the field from a purely subjective method toward an objective method - although there is still a considerable way to go to achieve this important goal -The foundational validity of a subjective method can only be established through multiple independent black-box studies appropriately designed to assess validity and reliability -Remarkably, there have been only two black-box studies that were intentionally and appropriately designed to assess validity and reliability - the first published by the FBI Laboratory in 2011; the second completed in 2014 but not yet published

Focus on mainly two types of evidence

Pattern and impression evidence -Includes any markings produced when one object comes into contact with another object, such as fingerprints, shoeprints, toolmarks, and tire treads. -It also includes pattern analysis, such as is used when evaluating handwriting, typewriting, and writing instruments Trace evidence -Specific types of trace materials that could be transferred during the commission of a violent crime -These trace materials include human hair, animal hair, textile fibers and fabric, rope, soil, glass, and building materials

Fingerprint comparison

class: -loops, whorls, arches minutiae

law enforcement and forensic science

theres a "fundamental conflict" in how science is used by the legal system -the classical goal of science is the production of truth, while the goal of law is the achievement of justice -the clients want good science and the truth if it will help their case. If good science and the truth will not help their case, they will willingly settle for poor science and something less than the absolute truth