Forensic Science

How do you fume with cyanoacrylate (super glue)? How does a fuming cabinet help?

-Typically used in fuming cabinet -Accelerate process with alkali or heat -Can also be used at the scene via a hand held wand that emits both cyanoacrylate and a fluorescent dye. -May refume if needed, but over fumed prints are ruined Helps speed up chemical fingerprint development.

What are Alternative Light Sources? How do they help visualize a latent fingerprint?

-Various types of alternative light used to illuminate fingerprints: -Oblique lighting -Bright white light (525 nanometers) -Lasers -UV lights & fluorescent powders -Colored filters & chemical developers

How are DNA markers inherited? How can DNA be used to determine paternity/maternity testing?

A genetic marker is a DNA sequence with a known physical location on a chromosome. ... DNA segments close to each other on a chromosome tend to be inherited together. Genetic markers are used to track the inheritance of a nearby gene that has not yet been identified, but whose approximate location is known. DNA paternity testing is the most accurate form of paternity testing possible. ... To conduct DNA testing, either a blood test known as Restriction Fragment Length Polymorphism (RFLP) or a procedure called a Buccal scrap is used. A swab is rubbed vigorously against the inside of the subject's cheek.

How are fingerprints compared and matched? What is the "ACE" method?

A latent examiner focuses on comparing "chance" fingerprints left accidentally at crime scenes or elsewhere, to possible source prints. A tenprint examiner, by contrast, compares fingerprints purposefully collected in controlled circumstances (such as at a police station) with those on file in a database. ACE is a simple explanation of the phases involved in perception and decision-making. ACE gives the expert specific phases of examination that can be used to document the perception, information- gathering, comparison, and decision-making that takes place during an examination of prints.

What are the different types of arches, loops and whorls? How do you identify them?

ARCHES- Two types Plain: ridges flow from one side to the other rising smoothly in center Tented: central upthrusting ridge or ridges meet at 90 degrees, intermediate between arch & loop Plain arch, tented arch, plain arch. LOOPS- Most common pattern 60% Features of a loop: Single delta (triangle shape) A core Recurving ridge Can open towards either side Left loop opens to left Right loop opens to right WHORLS- Four types: Plain Central pocket loop Double Accidental Level I: Basic pattern and ridge flow Level II: Minutiae, point by point as to type and location Level III: Pore shape, size and shape of edge features

How often is the actual perpetrator identified in DNA exoneration?

Actual perpetrator identified by DNA in ~50% of cases.

What is CODIS (Combined DNA Information System)? How does it work?

All states have legislation that mandate collection of DNA samples from offenders of particular crimes. CODIS allows local, state, and national crime laboratories to compare DNA profiles electronically CODIS can link: Offenders to crimes Crimes to each other Unsolved to solved crimes Missing persons to remains

What is AFIS? How does it work? How is the final determination of a match made?

Automated Fingerprint Identification System. AFIS is one forensic computer systems in the US: AFIS- Automated Fingerprint Identification System Computer generated matches are analyzed by trained fingerprint expert for final determination.

Define DNA, chromosome, gene, allele, genotype, phenotype, dominant, recessive, co-dominant, traits.

DNA- Double helix 2 chains of nucleotides held together by hydrogen bonds Hydrogen bonds are weak chemical/magnetic bonds Cromosome - A chromosome is a strand of DNA. Gene-A gene is a section of the chromosome that codes for a particular "thing", usually a protein. Allele-Different forms of a gene are called alleles Genotype- genes or alleles present Phenotype- physical or observable characteristic alleles Can be dominant, recessive, or co-dominant If two different alleles present, the one that is expressed (phenotype) is dominant. The other is recessive. Can be dominant, recessive, or co-dominant

What part is used for DNA identification? Which part has the most variation?

Determining the number of repeats of specific sequences is the basis of DNA identification. Variation in the ~98% of DNA that is junk DNA has no effect

How do cells divide? How many cell divisions do humans have each second? How does DNA replicate?

Every time a cell divides it's DNA must be duplicated. Humans have ~25 million cell divisions per second. DNA polymerase replicates the DNA.

What are the five most common causes of wrongful convictions? How many innocent people are in US prisons?

Eyewitness misidentification (~75%) Unvalidated or Improper Forensic Science (~50%) False confessions & incriminating statements (~25%) Snitches (~15%) Police and/or prosecutor misconduct Bad lawyering Estimated number of innocent people in the US prison system is 2% to 5%, or approximately ~50,000 to 120,000

What is mitochondrial DNA analysis? What does it indicate? What are it's uses, advantages, disadvantages?

Forensic advantage is the greater number of mitochondrial DNA molecules per cell, compared to one copy of nuclear DNA. Very time consuming & costly. Only done in certain circumstances.

What are ABO blood types? What are genotype & phenotype? How does ABO paternity testing work?

Four major ABO blood groups: Phenotype A = genotypes AA and AO Phenotype B = genotypes BB and BO Phenotype O = genotype OOPhenotype AB = genotype AB The two terms are often used at the same time to describe the same organism, but there is a difference between genotype and phenotype:An organism's genotype is the set of genes in its DNA responsible for a particular trait. An organism's phenotype is the physical expression of those genes. By examining ABO patterns, we can determine paternity and maternity. Especially helpful in cases of unknown parents, adoptions, or determining child paternity

What are fingerprints? When do they form? Do they change? Do any people have the same fingerprints?

Friction ridge skin found on fingers, palms, and soles of feet. Form early in embryonic development, unchanged through life. Fingerprint patterns are unique to each individual. Sweat from pores in skin transfers pattern to touched surface. No one has the same fingerprints, but can be very similar.

What % of DNA is genes? What % is junk? What % is repetitive sequences? What are repeats?

Genes make up only about 2% of our total DNA. Most of our DNA, over 98%, is considered "junk" DNA that has no known purpose. 30%-50% of human DNA is made up of repetitive sequences. Sequences vary in length from 2 to 80 bases. Repeated different numbers of times in different individuals. Determining the number of repeats of specific sequences is the basis of DNA identification.

After dusting a latent fingerprint, what should you do before trying to lift it? How do you lift a print?

However, fingerprint powders can contaminate the evidence and ruin the opportunity to perform other techniques that could turn up a hidden print or additional information. Therefore, investigators may examine the area with an alternate light source or apply cyanoacrylate (super glue) before using powders. Place the object on a clean, flat surface with the suspected location of the latent prints accessible. (Don't forget to wear gloves.) Choose the dark or light fingerprint dusting powder, according to which will provide better contrast with the color of the surface.

How does fuming develop a print? In what circumstances would you use iodine fuming?

However, in iodine fuming, natural body fats and oils in sebaceous material of a latent print temporarily absorb the iodine vapors. This results in a change in color, from clear to a dark brown, until the effect fades with time. Helps speed up chemical fingerprint development.

What are latent, patent, and plastic evidentiary fingerprints?

Latent- requires additional processing to be rendered suitable for comparison - processing is called development or enhancement Patent - clearly recognizable fingerprint that needs no processing - could be in grease, blood, dirt, or oil Plastic - also called an impression or indentation print- could be in tar, butter, silly putty

What are the different types of dusting powders? What is the best technique to dust for a print?

Many different types that are good in different situations **-Black fingerprint powders generally have best results -Magnetic powders and brushes are also available

What are minutiae? What are some examples? How many minutiae are required to determine a match?

Minutiae: ridge characteristics or details used for identification. Ridges form minutiae by: Ending abruptly - ending ridge Splitting into two ridges - bifurcation Being short in length - dot (island) Two bifurcations facing each other are known as an island (enclosure). At trial, authorities highlighted seven identifying characteristics — or points of minutiae — to link the cigarette print to Enderle's right ring finger. But seven points isn't usually enough to make a match, according to several fingerprint experts who say the industry typically calls for more.

What is Y Chromosome DNA analysis? What does it indicate? What historic case was it used in?

Most famous Y chromosome analysis showed that male descendants of Thomas Jefferson's family and male descendants of his slave Sally Hemings were related and shared a common male ancestor. Y Chromosome STR are the paternal counterparts to mtDNA Human Y chromosome is only passed on from father to son

Do chemical enhancement methods to develop a bloody print interfere with the ability to test for DNA?

Most processes for latent print chemical enhancement do not interfere with blood collection for DNA profiling

How many cells needed to test DNA? What are evidence sources for DNA? How accurate is DNA id?

Only 36 human cells necessary for PCR to amplify enough DNA to perform STR analysis. The biological material used to determine a DNA profile include blood, semen, saliva, urine, feces, hair, teeth, bone, tissue and cells. Not really 100%. The longer answer: While DNA is extremely good at identifying individuals, mistakes have happened.

What are the three general methods used to develop latent fingerprints?

Physical, Chemical, Special Illumination

What is Polymerase Chain Reaction (PCR)? How does it amplify (create more copies of) DNA?

Polymerase Chain Reaction (PCR). Enzymatic process that is makes multiple copies of a piece of DNA from a very small sample. (Amplify) Polymerase is the enzyme that attaches the new bases onto the DNA strands during replication.

What is RFLP? How did it work? What were it's drawbacks?

Restriction Fragment Length Polymorphism RFLP original method of DNA identification So RFLP analysis of a specific site usually results in two bands Drawbacks: It was time consuming and expensive Large repetitive sequences were susceptible to degradation by decomposition It required a large amount of DNA to work

What are restriction enzymes? What is gel electrophoresis?

Restriction enzymes cut DNA at specific base sequences, called recognition sequences. (e.g.GGATCC DNA molecule has charges, so it can be moved by an electrical current DNA fragments can be separated by size using gel electrophoresis. DNA fragments are placed in gel and electrical current applied DNA is moved by the electrical current Gel electrophoresis is a technique used to separate DNA fragments (or other macromolecules, such as RNA and proteins) based on their size and charge. Electrophoresis involves running a current through a gel containing the molecules of interest.

What are Short Tandem Repeats (STR)? How are they different from RFLP? What are their advantages?

Short Tandem Repeats (STR): Current standard in forensic DNA identification Like RFLP each chromosome will usually have a different number of repeats (maternal and paternal) but not always STR overall length are much shorter than those used for RFLP STR are less prone to degrade STR can often be recovered from bodies or stains that are extremely decomposed

Can you develop a fingerprint on wet objects? On the sticky side of tape?

Small particle reagent (SPR) is sprayed on print and adheres to lipids from prints, used on evidence that has been wet Developing latent fingerprints: Methods depend on circumstances: texture, composition, wet, sticky, etc. Use least destructive process first Use methods in an order that maximizes information Preserve prints by photography and lifting.

What is the structure/function of DNA? What are nucleotides, bases, base pairing? How is information stored?

Structure of DNA is the basis of replication. Base pairing provides the copying mechanism. Each strand acts as template for forming new base pairing (AT, GC). Sequences of bases repeating over and over.

How is DNA testing used in forensics?

The DNA profile was used to identify the perpetrator. As technology advances, forensic scientists are able to analyze smaller and smaller biological samples to develop a DNA profile. ... In some jurisdictions, a DNA sample is routinely taken from an arrestee during the process of booking and fingerprinting.

How many cells in the human body? How many chromosomes in a cell? Do all cells contain chromosomes?

The human body is composed of ~100 Trillion cells. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. You get one set of 23 chromosomes from your mom, and the other from your dad. The only human cells that do not contain pairs of chromosomes are reproductive cells, or gametes, which carry just one copy of each chromosome. ... Chromosomes vary in number and shape among living things. Most bacteria have one or two circular chromosomes

How were fingerprints used in the past? Were fingerprints in anthropometry? How are they used in forensics?

The use of fingerprints is centuries old, ancient civilization used fingerprints to sign pottery. Babylon used fingerprints on clay tablets for business transaction. China used clay thumb prints to "sign" documents. Persia, government documents have fingerprint impressions. Anthopometry: Early method of identification based on a number of body measurements (eg. head size, finger length, etc.) A person's fingerprints do not change over time. The friction ridges which create fingerprints are formed while inside the womb and grow proportionally as the baby grows.

What is DNA exoneration? How many people have been exonerated by DNA? On death row? Minorities?

There have been over 350 post-conviction DNA exonerations in United States. ~70 % of exonerated are minorities. Actual perpetrator identified by DNA in ~50% of cases.

What are the 3 basic fingerprint patterns? How do you identify them? What % of people have each of them?

arches, loops and whorls. Fingerprint Experts: Compare fingerprints from crime scene with known prints. Can also compare two unknowns to tie crimes together. Arches 5% of fingerprints. Loops 60% of fingerprints Right or left (open) (Radial or ulnar, depending on whether direction of slope of pattern is towards radius (thumb side) or ulna (pinky side). Whorls 35% of fingerprints most complex, can be plain, central pocket loop , double loop, and accidental.

What are five ways to improve our CJ system to reduce imprisoning innocent people?

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