Forensic Science Test #3

automobile paint--primer surfacer

epoxy-modified polyester or urethane; smoothes out surface to hide seams and imperfections; highly pigmented layer

analysis of evidence of explosives

everything arriving at the laboratory is examined microscopically to detect particles of unconsumed explosive; black powder and smokeless powders are relatively easy to locate in debris because of their characteristic shapes and colors; acetone extractions and water washings are normally performed and the solutions collected subjected to presumptive color tests--acetone extract can be concentrated and analyzed by TLC, HPLC, and GC-MS--considered screening tests; if sufficient quantities of explosives are recoverable, then confirmatory tests by infrared spectrophotometry or X-ray diffraction

Chinese

evidence exists that they used the fingerprint to sign legal documents as far as ~3000 years ago

questions concerning hair examination--Can Racial Origin of Hair be Determined?

examiner can sometimes distinguish between races; hair of European ancestry is rounder with evenly distributed pigments; hair of African ancestry is more oval or flat and has unevenly distributed pigments; hair of Asian ancestry is wider compared to hair of other races with larger sized pigment granules

ion mobility spectrometry

explosive residues are drawn into the ion mobility spectrometer where molecules are vaporized by application of heat; the molecules are ionized and then sent down a drift tube; their drift speed helps identify them; IMS used for screening, not confirmation; explosives detected include RDX, PETN, TNT, Semtex, Tetryl, NG, Nitrates, HMX, and others; drugs detected include Cocaine, Heroin, PCP, THC, Meth, Ecstasy, LSD, and others; 6-8 second analysis time

other bloodstain patterns--pools

occurs when blood collects in a level (not sloped) and undisturbed place; pools occurring on an absorbent surface may be absorbed and diffuse creating a pattern that is larger than the original pool; drying time of the pool is related to environmental conditions of the scene; small and large pools of blood can be used to estimate the amount of time that has passed since the blood was deposited; the edges of the stain will dry to the surface producing a phenomenon called *skeletonization*--skeletonization remains apparent even after the bloodstain is disturbed

contamination of DNA evidence--O. J. Simpson murder case

on June 12, 1994 police arrived at the home of Nicole Brown Simpson to find the bodies of O.J. Simpson's estranged wife and her friend Ron Goldman; a trail of blood led away from the crime scene; blood was found in Simpson's bronco, on Simpson's driveway, on a glove found outside his home, in the foyer of his home and on a sock in his bedroom; on June 17 arrangements had been made with the LAPD for O.J. Simpson to turn himself in as a suspect in the murders; Simpson failed to show at the designated time and the resultant 'white bronco chase' ensued lasting until late the same evening; on June 20, Simpson was arraigned and pleaded not guilty to both murders; the case went to trial on November 3, 1994; the prosecution presented evidence that linked Simpson to the crime scene including DNA typing of blood found in bedroom linked to Brown, blood in Bronco and a bloody glove linked to Brown and Goldman as well as hair, fiber and shoeprint analysis; the defense argued that Simpson was the victim of police fraud and sloppy internal procedures that contaminated DNA evidence; much of the incriminating evidence, bloody sock, bloody glove and blood in Bronco, was discovered by LAPD detective Mark Furman; on October 3, 1995 the jury found Simpson not guilty; in 1997, the parents of Goldman and the estate of Brown (represented by Nicole's father) brought a 'survivor suit' against Simpson; the jury of this civil trial awarded Brown and Simpson's children and the victim's parents $33.5 million compensatory and punitive damages in the wrongful death of Brown and Goldman

collection and preservation of fiber evidence

relevant articles of clothing must be packaged carefully in paper bags; each article must be place in separate paper bags to avoid cross-contamination; care must be taken to prevent articles from different people or different locations from coming into contact; such articles cannot even be placed on the same surface before packaging; carpets, rugs, bedding must be carefully folded to protect potential fiber evidence; car seats must be covered with polyethylene; knife blades must be wrapped to protect any adhering fibers; adhesive tape lifts of exposed body areas can reveal whether body was wrapped in a carpet or blanket; if investigator must remove fiber evidence from an object, clean disposable forceps should be used and fibers placed in folded paper that in then placed inside another container

paint binder

provides support medium for the pigments and additives; a polymeric substance

morphology of hair--shaft is composed of three layers--medulla

a cellular column running through the length of the hair; classified as continuous, interrupted or fragmented

John Dillinger

famous bank robber in the 1930's; hired some doctors to burn his fingerprints off with sulfuric acid; while recovering, he was betrayed by a woman; after he was shot to death, the morgue took his fingerprints and could still match them to fingerprints recorded from a previous arrest

comparing impressions--class characteristics

features which are unique to a group of objects; these are features reproduced by the manufacturing process and how we determine size and design

identification and comparison of manufactured fibers--other properties for examination

fibers are often somewhat crystalline, which causes birefringence; because fibers are long, this isn't always easy to see; excite the fibers with polarized light; rotate the light 90 degrees and see if the appearance changes

types of fibers

fibers may become important evidence in incidents that involve personal contact such as, homicide, assault, or sexual offenses in which cross-transfers may occur between the clothing of the suspect and victim; value of fibers as forensic evidence depends on the analyst's ability to narrow the origin to a limited number of sources or even to a single source; fibers can be derived from a natural source or be synthetically manufactured; fibers can have distinctive colors and profiles

morphology of hair--human head hair grows in three developmental stages--telogen

final growth phase where hair falls out

developing latent prints--dusting

fingerprint powders are found from a number of commercial sources; a fine powder is applied using a camel hair or fiberglass brush and sticks to the print; black dust is used for light surfaces and is usually just carbon powder; grey dust is for dark surfaces and is alumina powder; leather and rough plastics trap powder, so a magnetic-sensitive powder is often used; the Magna Brush has no bristles and can be removed from the cracks without disturbing the print; fluorescent powders can make prints easier to see; the fluorescing print is photographed to avoid having the color of the surface obscure the print

first principle of fingerprinting--fingerprint is an individual characteristic

fingerprints are not genetic, but are based on conditions in the womb and are permanent by the 17th week of development; the FBI has never found two identical fingerprints--not in the nearly 50 million fingerprints found in the FBI database; fingerprints are identified using small ridge characteristics (*minutiae*)

other techniques for visualization--chemically induced fluorescence

fingerprints can be treated with chemicals that will induce fluorescence when exposed to laser light; zinc chloride can be applied after inhydrin treatment or rhodamine 6G dye can be applied after cyanoacrylate fuming; alternately, a high-intensity quartzhalogen or zenon arc source can be used to induce fluorescence from perspiration residues

automobile paint--electrocoat primer

first layer applied to steel body of a car; uses epoxy-based resins; prevents corrosion

types of fibers--manufactured fibers--regenerated fibers

first machine-made fibers were manufactured from raw materials derived from cotton or wood pulp; cellulose is extracted from cotton or wood; depending on desired fiber, cellulose may be chemically treated, dissolved in an appropriate solvent, and spun into fibers; ex: rayon (1911), acetate, and triacetate

the shoe

footwear examiners study impression evidence created by the shoe's *outsole*; a shoe's outsole pattern, size, and design are created by the designer's vision and the manufacturing process

origin-of-impact patterns--area of origin

represents an approximation of the three-dimensional space from which the blood was projected; attempts to show the position of the victim at the time the stain-producing event took place; uses a combination of the area of convergence and the angle of impact

fiber comparison conclusions

"consistent with known fiber source"; "dissimilar to known fiber source"; "inconclusive comparison to known fiber source"; *cannot make a positive identification to a known fiber source to the exclusion of all others*

hair comparison conclusions

"microscopically consistent with known hair standard, could have originated from"; "dissimilar to known hair standard"; "inconclusive comparison"; *cannot make a positive conclusion with a hair comparison to the exclusion of all other sources*

digital imaging for fingerprint enhancement

*digital imaging* is the process by which a picture is converted into a series of square electronic dots called *pixels*; each pixel is assigned a number according to its intensity ranging from 0 (black) to 255 (white); prints can be input into a digital imaging system using a scanner, digital camera, or a video

other techniques for visualization--laser fluorescence

certain compounds *fluoresce* (emit visible light) when exposed to laser light

comparing impressions--identifying characteristics

characteristics that are unique and attributed to natural deviation and damage (wear and tear)

chemistry of fire--other forms of combustion

*glowing combustion* or smoldering occurs in the absence of flaming fire, heat is insufficient to pyrolyze the solid fuel--ex: red-hot charcoals; *spontaneous combustion* described a fire caused by a natural heating process in the presence of sufficient air and fuel--ex: hay stored in barns and rags soaked in certain oils (linseed oil) have been known to spontaneously combust

analytical techniques used in paint comparison--characterization of paint binders

*pyrolysis gas chromatography* has proven to be particularly valuable technique for distinguishing most paint formulations; paint chips as small as 20 um decomposed by heat and gaseous products separated by gas chromatography; the pattern is referred to as a *pyrogram*; the pattern of the pyrogram distinguishes one binder formulation from another; *infrared spectrophotometry* can also provide information onbinder composition of paint

Oklahoma City bombing

April 15, 1995 Timothy McVeigh rented a Ryder truck in Kansas; McVeigh and Terry Nichols filled it with ~5000 lb of a type of ANFO explosives; April 19 McVeigh detonated it in front of the Alfred P. Murrah Federal Building in Oklahoma City; the blast made a 28 ft wide, 7 ft deep crater; 168 people were killed--800 people were injured; McVeigh was stopped 90 minutes later for driving without a license plate and arrested for illegal weapons possession; before he was released, they linked him to the explosion; Nichols was sentenced to life in prison and McVeigh was sentenced to death--he was executed June 11, 2001 by lethal injections

central park jogger case

April 19, 1989, Tricia Meili left for a jog in Central Park at about 9 pm; at about 2 am she was found unconscious in the park; she had been raped, beaten, sodomized, and had lost 75% of her blood; she was in a coma for 12 days and had no memory of what happened when she awoke; earlier that night a group of 14 - 15 year old boys had been rounded up; some of the boys admitted to participating in the attack but later recanted their statements; five were charged with the crime despite the fact that none of the recovered semen could be linked to the defendants; two head hairs linked to the victim were found on one of the defendants; they were convicted and served from 7 - 13 years; Matias Reyes was arrested in August 1989 for murder, rape, and robbery; in January 2002 he confessed to the Central Park attack; his DNA matched that found at the crime scene; the convictions of the teenagers were overturned and in September 2014, the five wrongly convicted men received $41 million in a civil rights settlement

developing latent prints--Cyanoacrylate fuming

Cyanoacrylate is the generic name for Super Glue®; Cyanoacrylate fuming is used to develop prints in non-porous surfaces; the glue is heated and condenses on prints, leaving a permanent white residue; the fumes and object are kept within an enclosed chamber for several hours; the prints are often dusted to increase their contrast

structure of DNA--nucleotides

DNA contains four repeating units called nucleotides--Adenine (A), Guanine (G), Cytosine (C), and Thymine (T); each nucleotide is composed of a sugar and phosphate backbone and a nitrogen-containing base

Friedrich Miescher

DNA first isolated in 1869

polymerase chain reaction (PCR)

DNA replication held little interest to forensic scientists until the advent of this laboratory technique; it is a technique designed to copy or multiply DNA strands

significance of paint evidence

How certain can one be that two similar paints came from the same surface?; in statistical terms, if the crime scene paint sample and the paint standard/reference sample compare by-matching paint color, matching paint layers, matching paint binder formulation, matching elemental compositions of pigments-then the odds against the crime scene paint originating from another randomly chosen vehicle is approximately 33,000 to 1

Kary Mullis

In 1983 he significantly improved the copying of DNA using what he termed polymerase chain reaction, or PCR; his employer, Cetus, gave him a $10,000 bonus and they later sold the patent to Roche for $300,000,000; he received the Nobel Prize in 1993

developing latent prints--Iodine fuming

Iodine crystals are heated and form vapors (sublime)--these vapors turn purplish brown when they are absorbed into the sebaceous oils present in the print--Iodine is volatile and the color starts to fade soon--the colored print must be photographed

Mary Hardy Reeser--suspected spontaneous human combustion

Mary Hardy Reeser was a resident of St. Petersburg, FL; her landlady discovered her remains on July 2, 1951; her body was almost completely cremated except for an intact foot and shoe; all that remained of the chair she was seated in were the steel springs; her apartment was not burned much except there was evidence of high temperatures on the ceiling above her chair/remains; FBI report discounted spontaneous combustion and suggested that the wick effect was likely responsible--the wick effect requires that the clothing be ignited by an external flame--the body's own fat stores provide fuel to sustain the flame; ceiling damage seems to support FBI conclusion

developing latent prints--Ninhydrin

Ninhydrin reacts with amino acids to form a purple color; Ninhydrin is used for porous materials; the color can take up to two days to appear; the development can be hastened by placing in a warm, humid environment; prints as old as 15 years have been developed

methodology

STEP #1--analysis: look for identifying or wear characteristics like--bald areas, cuts/scratches, gouges; STEP #2--comparison

significance of paint evidence--Royal Canadian Mounted Police Forensic Laboratories

Since 1975, they have systematically gathered color and chemical information on automotive paints; the computerized database is known as PDQ (Paint Data Query)

obtaining DNA reference specimen

a court order is required to collect either blood or skin cells; at least 7 mL (7 cc) of blood preserved with EDTA and refrigerated is desired; buccal swab vigorously rubbed against the inside of the cheek; cells transferred to FTA card that entraps DNA and allows storage for at least ten years at room temperature

Will West incident

a man named Will West was incarcerated at Fort Leavenworth in 1903; they were quite surprised to find that, according to the Bertillon system, he was already there; fingerprints clearly distinguished the two prisoners

locating the fire's origin

a search of the fire scene must focus on finding the fire's origin, which will prove most productive in any search for an accelerant or ignition device--investigator may uncover evidence of separate and unconnected fires, investigator may find evidence of 'streamers' used to spread fire from one area to another--ex: arsonist may spread a trail of gasoline or paper to cause the fire to move rapidly from room to room; there are no fast and simple rules for identifying a fire's origin--normally fires generally move upward, most likely origin should be closest to the lowest point that shows the most intense characteristics of burning, sometimes a V-shaped pattern forms against a vertical wall as a fire burns upward, charring is expected to be more intenseon the bottom of furniture and shelves rather than top, normally carpets don't burn much; many factors can contribute to the fire from normal behavior--prevailing drafts and winds, secondary fires due to collapsing floors and roofs, the physical arrangement of the burning structure, stairways and elevator shafts, and holes in the floors, walls, and roof

other bloodstain patterns--drip trail pattern

a series of drops that are separated from other patterns, formed by blood dripping off an object or injury; stains form a kind of line or path; can show movement of the assailant or movement of the wounded victim; may lead to a discarded weapon or provide identification of the suspect; shape of the stains in the drop trail pattern can help investigators determine the direction and speed at which the person was moving (round spots = standing still or slow movement)

third principle of fingerprints--fingerprints have general ridge patterns that permit them to be systematically classified

all fingerprints are dived into three classes on the basis of their general pattern--loops, whorls, and arches; 60-65% of the population have loops, 30-35% have whorls, and ~5% have arches

collection and packaging of evidence of explosives

all materials collected for examination placed in airtight containers; articles collected from separate areas should be packaged separately; plastic bags should not be used to stored evidence suspected of containing explosive residues

chemistry of fire--combustion

all oxidation reactions, including the combustion of methane, liberate more energy than is required to break the chemical bonds between atoms; an *exothermic* reaction is a reaction that gives off heat energy; an *endothermic* reaction is a reaction that absorbs heat energy

significance of paint evidence--PDQ (Paint Data Query)

allows the analyst to obtain information on paints related to automobile make, model, and year; the database also contains paint layer colors, primer colors, and binder composition

identification and comparison of manufactured fibers--dye comparison

although two fibers may appear to have the same color when viewed under the microscope, compositional differences may exist in the dyes that were applied to the fibers; a visible light microspectrophotometer can be used to compare the color of fibers; a chromatographic comparison of the dye components can be performed by extracting dyes with a suitable solvent and spotting on a TLC plate for side-by-side comparison between questioned and standard/reference fibers

ammonium nitrate explosives

ammonium nitrate fuel oil mixtures (ANFO) have replaced commercial nitroglycerin-based dynamite because they are inexpensive and relatively safe to handle in many blasting related applications; 80% as effective as TNT; ammonium nitrate is commonly available in fertilizers; add ~6% fuel oil and mix; difficult to detonate

DNA typing--exons

are segments of DNA used for protein instructions

DNA typing--introns

are segments that are cut out

print patterns--arches

are subdivided into two distinct groups--plain and tented; *plain arches* are formed by ridges entering from one side of the print and exiting the other side; *tented arches* have ridges that form a sharp up thrust spike

the chemistry of explosions

an *explosion* is the product of combustion accompanied by the creation of gases and heat--the distinguishing characteristic of an explosion is the rapid rate of the reaction, the sudden buildup of expanding gas pressure at the origin of the explosion produces the violent physical disruption of the surrounding environment; detonation occurs so rapidly that oxygen in the air cannot participate in the reaction, thus, many explosives must have their own source of oxygen--chemicals that supply oxygen to a chemical reaction are known as *oxidizing agents*--ex: Potassium Nitrate (KNO3) is the oxidizing agent in black powder (75% KNO3, 15% charcoal, 10% sulfur), 3C + S + 2KNO3→ CO2↑+ N2↑+ K2S, trinitroglycerin combines the fuel and oxygen source in one molecule; consider the effect of confining an explosive charge to a relatively small, closed container--on detonation the explosive almost instantaneously produces large volumes of gases that exert enormously high pressures in the interior walls of the container, heat energy released by the explosion expands the gases even more causing even higher pressures (several hundred tons/in2), walls of the container will stretch and balloon under the pressure and eventually fragment and fly outward, the sudden release of the confined gases will compress layers of surrounding air as they move outward from the origin of the explosion with rates that can reach 7,000 mi/hr

taggants

an explosive 'taggant' program has been proposed to further enhance a bomb scene investigator's chance of recovering useful evidence at a post-explosion scene; tiny color-coded chips the size of sand grains would be added to commercial explosives during their manufacture; chips are made to both fluorescent and magnetic sensitive; taggant color sequence would indicate where and when the explosive was made; the International Civil Aviation Organization has mandated that a volatile taggant be added to plastic explosives (C-4) during their manufacture in order to facilitate the detection of these explosives--the volatile chemical known as 2,3-dimethyl-2,3-dinitrobutane (DMNB) is a current tag, the slow evaporation of the tag from plastic explosives can be detected by trained dogs or IMS--dogs and IMS can detect as little as 0.5 ppb DMNB in air

general features of bloodstain formation--direction and angle of impact

an investigator may discern the direction of travel of blood striking an object by studying the stain's shape; as the stain becomes more elliptical, the long axis ending in a point will indicate the direction of travel; it is possible on a smooth surface to determine the angle of impact by measuring the degree of circular distortion of a stain--sin A = width of stain/length of stain--where A is angle of impact

gas-air mixtures

another form of low explosive is created when a considerable quantity of natural gas escapes into a confined area and mixes with a sufficient amount of air; CH4+ 2O2→ CO2↑+ 2H2O; methane 5.3-13.9% in air explodes; rich mixtures explode; the unconsumed gas then starts a big fire; lean mixtures just explode without damage due to fire

DNA polymerases

are enzymes that assemble the new DNA strand

latent prints

are impressions caused by the transfer of bodily perspiration or oils present on the finger ridges to the surface of an object

DNA typing--tandem repeats

are introns that repeat (~30%); they are inherited; the repeated pattern stays the same between individuals; the number of repeats varies betweenindividuals

visible prints

are made when fingers touch a surface after the ridges have been in contact with something colored--like blood, paint, ink, or grease

plastic prints

are ridge impressions left in soft materials like putty, wax, soap, or dust

types of fibers--natural fibers

are wholly derived from plant or animal sources; fibers derived from animals are commonly encountered at crime scenes; ex: wool from sheep, cashmere from goats, fur fibers from rabbit, mink, and beaver, the most prevalent plant fiber is cotton

forensic investigation of arson

arson often presents complex and difficult circumstances to investigate; the contribution of the forensic analyst is only one aspect of a comprehensive investigative process that must establish motive, the modus operandi- the suspect's pattern of operation - and a suspect; arson is responsible for 25% of the fires in the US--results in $2 billion in damages every year--only 15% of the cases end in arrest; arson incidents are usually planned in advance; the perpetrator has left the crime scene long before any official investigation is launched; there is extensive destruction; forensic analyst's job is to identify chemical materials from scene and to reconstruct and identify igniters

detonators

bombs made with high explosives must be detonated by an initiating explosion--ex: blasting caps (Copper and Aluminum cases filled with lead azide and PETN or RDX) initiated with fuse or electric current

automobile paint--basecoat

colorcoat that resist weather, UV radiation, and acid rain

composition C-4

consists of RDX (91%), a plasticizer (which can be dioctyl adipate {DOA}, diethylhexyl, or dioctyl sebacate) (5.3%), a binder, which is usually polyisobutylene (2.1%), SAE 10 non-detergent motor oil (1.6%)

paint vehicle or solvent

controls viscosity

more bloodstain spatter patterns--void patterns

created where something was present to interrupt the blood spatter pattern; can help establish position of victim or assailant at the time of the incident

general features of bloodstain formation

crimes involving violent contact between individuals are frequently accompanied by bleeding and resultant bloodstain patterns; bloodstain patterns can provide valuable insights into events that occurred during the commission of a violent crime including, the direction from which blood originated, the angle at which a blood droplet struck a surface, the location or position of victim at the time a bloody wound was inflicted, the movement of bleeding individual at the crime scene, the minimum number of blows that struck a bleeding individual, the approximate location of individual delivering blows that produced bloodstain pattern

collection and preservation of biological evidence for DNA analysis

currently STR methods have changed what the crime scene investigator collects as evidence beyond the traditional dried blood and semen stains; DNA typing has been demonstrated with roughly 18 skin cells deposited on an object (touch DNA); contamination can be a major problem

short tandem repeats (STR)

currently this analysis has emerged as the most successful and widely used for DNA profiling; these are much shorter segments of DNA; sequences are 3 - 7 bases and repeat 3 - 11 times; segments are short, so PCR can be used; PCR provides great sensitivity ~100x less than needed for RFLP; short segments and improved sensitivity means that degraded samples may be analyzed; TH01 is a commonly used STR in forensic science--AATG is the repeating sequence--seven variants in the human genome containing five to eleven repeats--during a forensic examination TH01 is extracted from biological materials and amplified using PCR--the amplified STRs are separated using electrophoresis--an electric field is applied and the DNA segments move toward the opposite end of the gel--shorter pieces of DNA move faster--DNA pattern is examined for matches between band sets

DNA

deoxyribonucleic acid is the information carrier in the cells; has become an indispensable tool in forensic science

satellite spatter

describes small droplets of blood that are distributed around the perimeter of a drop or drops of blood and produced upon impact of the blood with the surface

structure of DNA: complementary base pairing

each nucleotide only binds with one other nucleotide--Adenine and Thymine make a pair, Guanine and Cytosine make a pair; base pairing tells us what the complementary strand of DNA will be for a certain sequence

searching for accelerants

fortunately, only under the most ideal conditions will combustible liquids be entirely consumed during a fire; liquids may seep into porous surfaces, cracks in floor, upholstery, rags, plaster, wallboard's, or carpet; if fire is extinguished with water, the evaporation rate of the combustible liquid may be slowed because water cools and covers materials through which the combustible liquid will have soaked; portable hydrocarbon detector is an excellent screening device for checking suspect samples at the fire scene; some dogs are trained to recognize the odor of hydrocarbon accelerants

analyzing digital images

frequency analysis is used to identify periodic or repetitive patterns such as lines or dots that interfere with the appearance of the image; patterns can be identified and diminished or eliminated to enhance the appearance of the fingerprint; interfering color backgrounds can be removed to make the print stand out; scaling and resizing tools in the software allow portions of the print to be examined at a time; comparisons can be made between file prints and print in question; visual fingerprint in blood on fabric is digitally enhanced to eliminate underlying fabric pattern

other impressions

from time to time, impressions of other kinds are left at a crime scene; this evidence may take the form of a shoe, tire, or fabric impression--ex: shoe impression left on carpet at a scene of a burglary, hit-and-run victim's garment may have come into contact with an automobile

paint pigments

give color and opacity to paint; usually mixture of inorganic and organic compounds

general features of bloodstain formation--surface texture

greatly influences the bloodstains; harder and nonporous surfaces (like glass and tile) will result in stains with smoother edges and less satellite spatter; rough surfaces (like carpet, textured sheetrock, wood) will result in irregular shaped stains with more satellite spatter

collection and preservation of hair evidence

hair from different parts of the body vary significantly in its physical appearance; forensic comparisons either involve head or pubic hair; require 50 full length hairs from the scalp to ensure representative sampling and 25 full length pubic hairs, either pulled out (preferred) or clipped at the skin line; in rape cases, all foreign hair should be combed/collected before taking standard/reference samples from the victim

morphology of hair

hair is encountered as physical evidence in a wide variety of crimes; hair is an appendage of the skin that grows out of a *hair follicle*; the hair extends from the root embedded in the follicle, continues into the shaft and terminates in the tip end

DNA sources

hat; eyeglasses; plastic toothpick; dirty laundry; cigarette butt; stamp, envelope; blanket; bite mark; fingernail; bottle or can; toothbrush; comb; earplugs; gum; cell phone

print patterns--whorls

have type lines and at least two deltas are divided into four distinct groups; *plain whorls* and *central pocket whorls* have at least one ridge that makes a complete circuit creating an oval, circle, or spiral; the *double loop* is made up of two loops; the *accidental loop* is made up of two or more patterns

questions concerning hair examination--Can Body Area from which Hair Originated be Determined?

head hair = generally round with a missing or fragmented medulla, show little diameter variation; pubic hair = generally flat or oval with a continuous medulla, wide diameter variation; beard hair = often triangular in cross section, blunt tips from cutting or shaving

chemistry of fire--combustion--oxidation reactions can differ in several aspects

heat necessary to initiate the reaction; common fuels have different *ignition temperatures*, that is, temperature at which a fuel spontaneously ignites; speed of the reaction increases when molecules of fuel and oxygen are volatile and able to collide frequently; for liquid fuels, the fuel temperature must be high enough to vaporize the fuel to support combustion--the minimum temperature is called the fuel's *flash point*; for solid fuels, the temperature must be high enough to decompose the solid into gaseous products in a process called *pyrolysis*

convection

heat transfer through moving liquid or gas; hot gaseous product rise upward in a structural fire becoming a radiant heat source

radiation

heat transfer through space via electromagnetic radiation; surfaces that face radiant heat source will burst into flames when their ignition temperature is reached

Phoebus Levene

identified the base, sugar and phosphate components of DNA in 1929

lifting impressions

if the impression is made in a light deposit of dust or dirt, the impression can be preserved in a manner analogous to lifting a fingerprint; footprints or other marks left in dust can be lifted using gelatin sheets or electrostatic lifters (Mylar sheet is placed over the impression and charged with static electricity causing the dust to stick to the sheet); large areas can be checked; dust and light dirt impressions can also be enhanced through chemical development; 8-Hydroxyquinoline will fluoresce under ultraviolet light when it reacts with calcium, magnesium, iron, aluminum, and other metallicions

Why is impression evidence an important forensic tool?

impression evidence can establish--1. positive identification, 2. the number of individuals present at a scene, 3. the direction in and out of a scene 4. it can link different scenes together

Henry Fauld

in 1880 this Scottish physician suggested the use of fingerprints for identification

Sir Edward Richard Henry

in 1897, he proposed a classification system used to file prints in a logical searchable order

Federal Bureau of Investigation

in 1904 this was formed; the fingerprint records of Leavenworth and the Bureau of Investigation were merged to create the nucleus of the identification records

Oswald Avery

in 1943 he showed that traits were transferred by DNA

Alfred Hershey and Martha Chase

in 1952 they confirmed that DNA is the genetic material

James Watson and Francis Crick

in 1953 they proposed the double helix structure of DNA based on information from Rosalind Franklin showing that the bases were always paired; they received the Nobel Prize in 1962

"Son of Sam" shootings and killings

in 1976 couples and women in New York City were being shot; the attacker used a 0.44 caliber Bulldog revolver; the victims seemed random; 9 were shot--3 were killed; survivors described the suspect as a white male, 25-30, 5'9" tall, medium build, dark hair; April 17, 1977 two more people were killed--the killer left a letter for the police; profilers determined that the killer was a paranoid schizophrenic, considered himself possessed by a demon, was a loner, and had difficulty with relationships; they received thousands of tips--none were useful; July 31, 1977 the final victims were shot--there were several witnesses

Roscoe Pitts aka Robert Phillips

in October 1941 police in Austin arrested a man with no fingerprints; he said his name was Roscoe James Pitts; he had scars on his chest; police in North Carolina in the process of investigating a crime, talked to a known criminal's girlfriend that told them her boyfriend had gone to New Jersey to have his fingerprints removed; the FBI found the New Jersey doctor that had surgically altered the man's fingerprints and confirmed that the man's name was Robert Phillips; enough of his prints remained to confirm his identity; he was arrested

New York City Civil Service Commission in 1901

in the United States, the first systematic and official use of fingerprints for personal identification was adopted by this

high explosives

include dynamite, TNT, PETN, and RDX, have detonation velocities between 1000-8500 m/s; classified as primary and secondary explosives based on their sensitivity to heat, shock, or friction; *primary explosives* are ultra sensitive to heat, shock, or friction and detonate violently instead of burning (ex: lead azide, lead styphnate, diazonitrophenol); *secondary explosives* are insensitive to heat, shock, or friction and burn rather than detonate in open air (ex: dynamite, trinitrotoluene (TNT), pentaerythritoltetranitrate (PETN), and cyclotrimethylenetrinitramine (RDX)

morphology of hair--human head hair grows in three developmental stages--anagen

initial growth phase during which follicle actively produces hair; lasts up to six years; root is attached to follicle; if hair is pulled out in the this phase, it may have a follicular tag (translucent piece of tissue rich in DNA)

1904 World's Fair in St. Louis

instruction in fingerprint identification was given to American police officials as a part of this

impact bloodstain spatter patterns--classifying impact spatter

investigators classify impact spatter based on the velocity of the blood droplet; in general, as the velocity of the force of impact on the source of blood increases, so does the velocity of the blood emanating from the source; they are categorized into low, medium, and high velocity spatter; droplet size decreases as velocity increases

documenting bloodstain pattern evidence

investigators note, study, and photograph each pattern and drop; two common methods for documenting bloodstain patterns place attention on the scale of the pattern--the *grid method* involves setting up grid of squares of known dimension over the entire pattern using strings and stakes, and the *perimeter rule* involves setting a rectangular border of rulers around the pattern

developing latent prints--physical developer

is a silver nitrate--based liquid reagent; very useful for developing prints in porous items that have been wet at one time; it washes away proteins and other evidence on the surface, so should be used after other methods have been tried

back spatter

is backward from the source potentially depositing on the object or individual creating the impact; on entry

primary classification of fingerprints

is part of the original Henry system and provides the first classification step in the FBI; each time a whorl pattern is found, it is assigned a numeric value--16 the first pair, 8 the second, 4 the third, 2 the fourth, and 1 on the fifth; this classification alone generates 1024 groups; 25% of the population falls into the 1/1 category

chemistry of fire--energy

is the combined ability or potential of a system or material to do work; takes many forms including heat energy, mechanical (kinetic) energy, chemical energy, and electrical energy; ex: when methane is burned or combusted, chemical energy stored in the methane bonds is converted into energy in the form of heat and light

low-velocity spatter

less than 1.5 m/s (<5 ft/s); stains are usually more than 3 mm in diameter; usually from drips

explosions and explosives

like arson investigation, bomb investigation requires close cooperation of a group of highly specialized individuals trained in bomb disposal, bomb-site investigation, forensic analysis, and criminal investigation; the forensic analyst must detect and identify explosive chemicals recovered from the crime scene as well as identify detonating mechanisms

locating prints

locating visible or plastic prints at the crime scene normally present little problem to the investigator; locating latent prints requires the use of techniques to render the prints visible; hard, nonabsorbent surfaces (glass, mirror, tile, metal) require different techniques than soft, porous surfaces (paper, cloth, cardboard); prints on hard surfaces can be treated with a powder or superglue; prints on soft surfaces must be chemically treated

other bloodstain patterns--flow patterns

made by drops or large amounts of blood flowing by the pull of gravity; may form from single drops or large volumes of blood coming from active bleeding; flow direction shows movement ofobjects while flow was still in progress; interruption of pattern may be helpful in accessing the sequence and passage of time between flow andits interruption

sex identification using STRs

manufacturers of commercial STR kits used by forensic laboratories provide one additional piece of information in addition to the thirteen STR types--the sex of the DNA contributor; focuses attention on the *amelogenin gene* found on both the X and Y chromosome; amelogenin gene codes for most abundant protein composing tooth pulp; Y chromosome version is longer than X; males will show two bands (one from X and one from Y chromosome) and females only one band (only from X chromosome); kits are also available that allow forensic laboratories to type STRs located only on the Y chromosome (Y-STRs); useful for analyzing blood, semen and saliva samples originating from more that one male suspect; each unrelated male involved will show one band for each STR; females will show no bands; fraternal brothers should have identical Y-STRs

identification and comparison of hair--considerations in hair examination

medulla and distribution, shape and color of pigment granules can be compared; Is hair of human or animal origin?; Does hair recovered at crime scene belong to suspect?; Does hair match color, length, diameter?; Is hair is dyed or bleached? (Hair grows ~1 cm / month, so time since it was colored can be determined)

RDX

military explosive; can be made from hexamine; detonates at ~20,000 mph; very stable; very powerful; Research Department Explosive developed by Britain in 1943; can be made from nitric acid and hexamine (solid fuel tablets commonly used in camp stoves)

PETN

military explosive; fairly stable; very powerful; is in primacord

capillary electrophoresis

modern instrumentation for separating STRs use a capillary rather than a gel; provides higher resolution for DNA separation; important if more than one type of DNA is present in a sample

analysis of flammable residues

most arson's are initiated by petroleum-distillates, such as gasoline and kerosene, which are composed of complex mixtures of *hydrocarbons*; gas chromatography is used to separate the hydrocarbon components and produce a chromatographic pattern that is characteristic of the particular petroleum product; the airtight container can be heated to volatilize traces of any flammable substances and the vapor in the container *headspace* can be sampled using a syringe and then injected into the gas chromatograph

types of fibers--manufactured fibers--synthetic fibers

most fibers currently manufactured are produced solely from synthetic chemicals; ex: nylons (1939), polyesters, and acrylics

identification and comparison of manufactured fibers--microscopic examination

most often the forensic analyst will receive a limited number of fibers for identification and comparison; the analyst must resort to side-by-side comparison of the standard/reference and crime-scene fibers; most important step in examination is comparison of color and diameter; Are lengthwise striations present?; Delustering particles (titanium dioxide) present on fiber surface?; cross-sectional profile can also be compared

print patterns--loops

must have one or more ridges entering from one side of the print, recurving, and exiting from the same side; *ulnar loop* opens toward the little finger; *radial loop* opens toward the thumb; area of the pattern is surrounded by two diverging ridges called *type lines*; the point of divergence is called *the delta*; the *core* is the center of the pattern

case study--Dr. Stephen Scher murder trial

on June 2, 1976, Dr. Stephen B. Scher and family friend attorney Martin T. Dillon were skeet shooting while staying at Dillon's hunting cabin near Montrose, PA; Dr. Scher told police that Mr. Dillon fell causing the shotgun he was carrying to fire into his chest; Mr. Dillon's death was ruled an accident; in 1978, Dr. Scher married Dillon's widow, Patricia and moved to North Carolina; Mr. Dillon's father was suspicious of the circumstances surrounding his son's death; in 1989 he hired an expert in crime scene reconstruction who concluded the death could not have been an accident; in 1992, Dr. Scher's boots taken two days after the shooting were sent to the FBI for analysis; examinations of the bloodstain patterns revealed that Scher's boots bore the unmistakable spray of high-velocity impact blood spatter indicating that Scher was within an arm's length of Dillon when he was shot; in 1995, Mr. Dillon's father prodded authorities to exhume his son's body; the pathologist stated that the shape and angle of the chest wound and the lack of powder burns indicated that Mr. Dillon could not have shot himself; in September 1997, Dr. Scher was brought to trial for the murder of Martin Dillon; during the trial Dr. Scher acknowledged having an affair with Patricia Dillon at the time of her husband's death; on October 22, 1997, the jury found Dr. Scher guilty of first degree murder; he was sentence to life without parole; in 1998, Patricia Scher was found guilty of lying under oath and received 15-months probation, a $500 fine, and 50-hours of community service; Dr. Scher died of natural causes in prison on August 9, 2010

a cautionary tale--the Madrid train bombing

on March 11, 2004 a coordinated series of bombs went off on commuter trains in Madrid, Spain; 191 were killed and 2050 were wounded; there were 13 bombs on 4 different trains' ten of the bombs went off within 3 minutes of each other; a bag containing detonators was found with a fingerprint on it; the fingerprint was matched to Brandon Mayfield, a Muslim convert, who had served in the US Army and was a lawyer' he was taken into custody on May 6 without charges; travel records showed that he had not been to Spain for over 11 years; on May 24 police in Spain arrested Ouhnane Daoud, an Algerian national--Ouhnane's prints matched those on the plastic bag; the FBI threw out the case against Brandon Mayfield and he was released within hours; the FBI formed an international committee of distinguished latent-print examiners and forensic experts to review the analysis performed at the FBI laboratory and make recommendations that would prevent this type of error in the future; Mayfield sued the government and received an estimated two million dollars

preservation of developed prints

once the latent print has been visualized, it must be permanently preserved for future comparison and possible use in court as evidence; a photograph must be taken before any further attempts at preservation (1:1 scale); if the object is small enough, the print is covered with cellophane to protect it from damage; the print is *lifted* using an adhesive tape if the print has been visualized with a dusting powder; Cyanoacrylate prints are permanent and are not lifted

automobile paint

one of the most common types of paint examined in the crime laboratory is finishes from automobiles; manufacturers apply a variety of coatings to the body of an automobile, which adds significant diversity and contributes to the forensic significance of automobile paint comparisons

forensic examination of paint--composition of paint

paint as physical evidence is perhaps most frequently encountered in hit-and-run and burglary cases; paint spread onto a surface dries into a hard film consisting of pigments and additives suspended in a binder

collection and preservation of paint evidence

paint chips are most likely to be found on or near people or objects involved in hit-and-run incidents; paint chips must be collected from garments and road surface to keep paint chips intact; tweezers may be used to pick up paint chip or a piece of paper may be used to scoop up paint chip; for hit-and-run cases, a standard/reference sample (1/4 inch) must be taken from undamaged area as close to the area of the car that is suspected to have contacted the victim as possible to avoid differences with paint fading or repainting; if two vehicles are involved in hit-and-run, then foreign paint as well as underlying original paint layers must be removed from each vehicle

more bloodstain spatter patterns--expirated blood patterns

pattern created by blood that is expelled from the mouth or nose from an internal injury; shows signs of high velocity spatter; can have bubbles of air in drying blood that can create a pattern that can be differentiated from other types of blood stains; often lighter in color if blood was diluted with saliva; presence of salivary amylase and oral bacteria may be detected

more bloodstain spatter patterns--gunshot spatter

patterns are characterized by both forward spatter (from exit wound) and back spatter (from entrance wound); amount of back spatter depends on location of injury, size of wound, and distance between victim and muzzle of the weapon; depending on distance, some back spatter may deposit on gunman or enter the gun muzzle (called drawback effect)

more bloodstain spatter patterns--cast-off spatter

patterns are created when a blood-covered object flings blood in an arc onto a nearby surface; occurs when an individual pulls a bloody object or fist back between blows to a victim; sharp objects produce smaller droplets and blunt objects produce bigger droplets; back swing produces larger droplets than the forward swing; number of patterns = number of blows

more bloodstain spatter patterns--arterial spray spatter

patterns are created when a victim suffers an injury to a main artery or the heart; commonly the pattern will show large spurted stains each time the heart pumps; will also see satellite spatter and flow pattern due to the large volume of blood; stain will show the victim's movement; blood pressure is initially 1-3 psi causing smaller droplets; decrease in blood pressure over time will cause larger, heavier staining

other bloodstain patterns--swipe patterns

produced by the movement of a bloody object across a surface; generally lightens and 'feathers' as the pattern moves away from the initial contact point; the direction of the bloody transfer may show movement of the suspect or victim through the crime scene

performance of PCR on a DNA segment

short sequences of DNA on either side of the region must be identified; these short DNA sequences are called *primers*--primers are 20 - 30 base pairs long and tell the polymerase where to start copying; primers combine or *hybridize* with DNA strands when temperature is lowered; temperature raised and polymerase directs the extension of primers

RFLP drawbacks

significant amount of starting material required (DNA segments cut by restriction enzymes too long for PCR); the fragments analyzed are long, so sample degradation can be a problem; labeled DNA probes can be expensive

primary explosives

silver fulminate--used in those pop snappers; sodium azide--was used in air bags; mercury fulminate--used in blasting caps

conduction

solids with loosely held electrons move heat through conduction (ex: metals - beams, nails, fasteners, bolts); solids with tightly held electrons are poor conductors and are called *insulators* (ex: wood)

significance of paint evidence--Law Enforcement Standards Laboratory at the National Institutes of Standards and Technology (NIST)

starting with the 1974 model year, they collected and disseminated to crime laboratories auto paint samples from US domestic passenger cars

origin-of-impact patterns

study of spatter patterns can offer investigators clues to help determine the origin of blood source and the position of the victim at the time of impact

low explosives

such as black and smokeless powders, decompose relatively slowly at rates up to 1,000 m/s--suitable as propellants for ammunition or skyrockets, can be dangerous when confined to small containers; *black powders*--(75% KNO3, 15% carbon, 10% sulfur)--burns when not confined (used in safety fuses)--explodes when confined; *smokeless powders*--(Nitrocellulose)--only explodes when confined; safety warning!!!--in the book it mentions potassium chlorate mixtures--it mentions that it might be combined with sulfur, carbon, sugar, starch, or magnesium filings--these are very dangerous combinations that will explode when you don't want them to--many combinations are shock sensitive--*never mix them*

triacetone triperoxide (TATP)

synthesized from acetone, hydrogen peroxide, and an acid catalyst; discovered in 1895 and used in many terrorist bombings; friction and impact sensitive; very potent; Richard Reed--'shoe bomber'--2006; dimer is less stable than the trimer--neither is stable; often mixed with smokeless powder to make acetone peroxide nitrocellulose (APNC)

polymers

synthetic fibers became a reality when scientists developed a method for synthesizing long-chained molecules; all fibers (natural and synthetic) are these; they are long chains of molecules arranged in repeating units called monomers

Alphonse Bertillon

the French police expert that came up with a system in 1883 for fingerprint identification; the system was called *anthropometry*--involved photos and measurements of many different areas of the body

origin-of-impact patterns--area of convergence

the area on the two-dimensional plane from which the drops originated; can be determined by drawing straight lines through the long axes of several bloodstains; multiple patterns will be produced when an object impacts a blood source many times

searching the fire scene

the arson investigator should begin searching a fire scene for signs of arson as soon as the fire has been extinguished; most arsons are started with petroleum-based *accelerants*; the most common accelerants are gasoline and kerosene; containers capable of holding an accelerant arouse suspicion; ignition devices can be as simple as a candle or as sophisticated as a time delayed device; a common telltale sign of arson is an irregular burn pattern on the floor or ground resulting from pouring accelerant onto the surface

analytical techniques used in paint comparison--characterization of pigments

the elements that constitute the inorganic pigments of paints can be identified by a variety of techniques--emission spectroscopy, neutron activation analysis, x-ray diffraction, x-ray spectroscopy; some elements are relatively common to all paints and have little forensic value, others are less frequently encountered and provide excellent points of comparison between paint specimen

chemistry of fire--oxidation

the fundamental chemical reaction of fire is oxidation--the burning of methane gas and the rusting of iron are both examples of oxidation reactions

DNA at work

the genetic code stored in DNA directs the production of proteins; proteins are made by linking amino acids; each amino acid is coded by a sequence of three nucleotides; ex: the amino acid alanine is coded by the combination of C - G - T; the amino acid phenylalanine is coded by A - A - T

ridge characteristics

the identity, number, and relative location of ridge characteristics impart individuality to a fingerprint; in a judicial proceeding, a point-by-point comparison must be demonstrated by an expert, using charts in order to identify an individual

United States v. Byron C. Mitchel

the judge upheld the admissibility of fingerprints as scientific evidence and ruled that 1) human friction ridges are unique and permanent and 2) human friction ridge skin arrangements are unique and permanent

morphology of hair--shaft is composed of three layers--cortex

the main body of the hair shaft with pigment granules that give hair its color

Automated Fingerprint Identification System (AFIS)

the manual system of classification was used by law enforcement until 1970 when computer technology made possible the classification and retrieval of fingerprints; in 1999, the FBI initiated full operation of the Integrated Automated Fingerprint Identification System; fingerprints are converted into digital images; the computer finds bifurcations and ridge endings and stores the relative position and orientation of these minutiae; the computer uses a search algorithm to determine the degree of correlation between the location and relationship of the minutiae for both search and file prints; the matches have to then be compared by a trained expert to see if they really are a match

fundamentals of crime-scene reconstruction

the method used to support a likely sequence of events at a crime scene by observing and evaluating physical evidence and statements made by individuals involved with the incident; includes--documentation of crime scene through photographs, sketches, and notes; involves law enforcement personnel, medical examiner, forensic scientist, and trained CSI

microscopic examination of paint

the microscope has traditionally been and remains the most important instrument for locating and comparing paint specimen; the importance in layer structure of paint evidence cannot be overemphasized; when paint specimen possess color layers that match in number and sequence of color, the forensic analyst can then begin to relate the paints to a common origin; diverse chemical compositions of modern paints provide additionalpoints of comparison between specimen

chemistry of fire--combustion--the mixture of fuel to oxygen is important to sustain combustion

the mixture only burns if the ratio of fuel to oxygen lies within a certain range called the *flammable range*; ex: for gasoline, the flammable in the range of 1.3 -6.0% gasoline vapor to oxygen (air)--below this range the fuel-air mixture is too lean and above this range it is too rich

impact spatter

the most common type of bloodstain pattern found at a crime scene

collection and analysis of evidence of explosives

the most obvious characteristic of a high or contained low explosive is the presence of a crater at the origin of the blast; once crater is located, all loose soil and other debris must be immediately removed from the interior or the hole and preserved for laboratory analysis; wood, insulation, rubber, and other soft materials near the blast origin often collect traces of the explosive; metal objects near the blast may also carry explosive residues; any item foreign to the blast site should be collected; efforts should be taken to avoid contaminating the scene including all personnel wearing disposable gloves, shoe covers, and overalls

anthropometry

the practice of rested on the several premises--the dimensions of the human bone system remained unchanged from age 20 to death and no two individual skeletons were alike; Bertillon recommended taking 11 measurements including height, reach, trunk, head width/length, cheek, ear, length of left foot, and left forearm among others

preserving impressions

the primary consideration in collecting impressions at the crime scene is the preservation of the impression or its reproduction for later examination in the forensic laboratory; impression is first photographed from several angles using lighting (including a scale) to show observable details of the impression; if the impression is on a readily recoverable item (paper, glass, floor tile), the original impression should be transported intact to the forensic laboratory; if the original impression cannot be submitted to the laboratory, then the investigator must preserve the impression

advantages of PCR

the primers make PCR very specific; you can amplify the desired fragments even when there is a lot of contamination; when repeated 30 times, you will have millions of copies, even if you started with one copy; from the forensic scientist's viewpoint, PCR offers the distinct advantage in that it can amplify minute quantities of DNA found in blood, semen, and saliva stains

STR probabilities

the probability of identifying someone uniquely increases with the number of STRs you use--3 STRs=1 in 5000; 6 STRs=1 in 2,000,000; 9 STRs=1 in 1,000,000,000; 13 STRs=1 in 575,000,000,000,000

morphology of hair--shaft is composed of three layers--cuticle

the scale structure covering the exterior of the hair

second principle of fingerprinting--a fingerprint remains unchanged during an individual's lifetime

the skin is composed of layers of cells--the outer layer being the *epidermis* and the inner layer being the *dermis*; the boundary between the epidermis and dermis is made up of cells called *dermal papillae*--the shape of the dermal papillae determines the ridge patterns on the skin surface; each skin ridge is populated by a single row of sweat gland pores; when a finger touches a surface, perspiration and amino acids are transferred to the surface creating a *latent fingerprint* of the ridge pattern

forward spatter

the spatter directed outward and away from the source; on exit

types of explosives

the speed at which explosives decompose varies greatly from one to another and permits their classification as low and high explosives; in *low explosives*, the speed of decomposition is called the speed of deflagration (burning); in *high explosives*, the speed of decomposition is called the speed of detonation (creation of a supersonic shockwave within the explosive charge)

polymerase chain reaction (PCR)--DNA replication

the synthesis of new DNA from existing DNA begins with the unwinding of the DNA strands of the double helix; each strand is exposed to a collection of free nucleotides; the nucleotides are assembled in the proper order (as dictated by base pairing) to yield an identical copy of the original DNA; many proteins and enzymes are involved in the unwinding, keeping the two strand apart and assembling the new DNA strands

DNA typing with STRs

the thirteen STRs chosen for standardization are non-overlapping in size to ensure they can be viewed clearly on a gel

vapor concentration

the vapor created by heating the airtight container can be collected and concentrated using a charcoal strip; traces of accelerant absorbed into the charcoal can be recovered by washing it with a small volume of solvent

wear in shoes

the way and extent to which a shoe wears is due to many factors including--person's foot size, shape, and biomechanical function, occupation, habits, weight body type, shoe style, shoe materials, surfaces the shoe has been worn over; wear can appear in shoes as--cuts, gouges, bald areas, tears, stone holding

wear in tires

the way and extent to which a tire wears is due to many factors including--improper inflation, balance, toe adjustment, or camber adjustment, rubber type/components, driving habits, surfaces the tire has been driven over; wear can appear in tires as--cuts, gouges, bald areas, tears, stone holding, exposed tie bars, cupping, feathering

multiplexing

there are hundreds of STRs found in human DNA; the more STRs forensic scientists can characterize, the smaller the percentage of the population from which these STRs can arise; using several STRs is known as multiplexing; in the United States, the forensic science community has standardized on thirteen (13) STRs for entry into a national database known as the Combined DNA Index System (CODIS)

analytical techniques used in paint comparison

there are more than one hundred automobile production plants in the United States and Canada; each can use one paint supplier for a particular color or vary suppliers during a model year; although a paint supplier must maintain strict quality control over a paint's color, the batch formulation of any paint binder can vary

obscuring of fingerprints

there has been no lack of effort on the part of some criminals to obscure their fingerprints; if an injury reaches deep enough (2mm beneath the skin's surface) to damage the dermal papillae, a permanent scar will form; the most publicized attempt to obliterate fingerprints was attempted by notorious gangster John Dillinger who tried to burn his fingerprints off using acid--his efforts proved fruitless

Francis Galton

this Englishman published a book in 1892 about using fingerprints as a unique identifier--assigned three pattern types loops, arches, and whorls

timeliness of fire investigation

time constantly works against the arson investigator; any accelerant residues that remains after a fire is extinguished may evaporate within a few days or even hours; safety and health conditions may necessitate that cleanup and salvage operations begin as quickly as possible; accelerants in soil and vegetation can be rapidly degraded by bacterial action

the tire

tire track examiners study impression evidence created by the *tread area*; a tire's tread area design and size are created by engineering requirements and the manufacturing process; tires are created using rubber and a molding process; this means that all tire treads created by a single mold will look the same

morphology of hair--human head hair grows in three developmental stages--catagen

transition stage between anagen and telogen phases

collection and preservation of arson evidence

two or three quarts of ash and soot debris must be collected at the point of origin of the fire, collection should include all porous materials and all other substances thought to likely contain flammable residues (wood flooring, rugs, upholstery, and rags), specimen should be packaged immediately in airtight containers so possible volatile residues are not lost through evaporation, fluids found in open bottles or cans should be collected and sealed; even containers appearing emptymay contain trace amounts of liquid; substrate controls should be collected from another area of the fire scene (ex: if carpet is collected at the point of origin of a fire), the investigator should collect unburnt carpet from another of the room, helps rule out detection of cleaning fluids from normal cleanings that may leave trace volatiles, helps identify breakdown products of carpet that may be mistakenly identified as accelerant; the scene should be thoroughly searched for igniters, the most common igniter is a match--other types of devices used to start a fire include burning cigarettes, firearms, ammunition, mechanical match striker, electrical sparking devices, and 'Molotov cocktail'

mitochondrial DNA--sequencing

two regions of mtDNA have been shown to be highly variable in the human population; hypervariable region I (HV1) and hypervariable region II (HV2); the A-T-G-C base pair order is determined in a process known as sequencing; mtDNA database maintained by FBI; mtDNA used to identify human remains (see Vietnam War's Unknown soldier First Lt. Michael Blassie, page 281)

mitochondrial DNA

typically forensic investigation are carried out on DNA located in the cell nucleus; DNA is also located in the cell mitochondria; *mitochondria* are the energy factories of our cells; every cell has hundreds to thousands of mitochondria; each mitochondrion has several loops of DNA designated at *mtDNA*--mtDNA is solely inherited from the mother--mtDNA may be used when nuclear DNA may be present in small quantity (in hair shaft) or in extremely degraded samples

heat transfer

understanding this becomes important in understanding how and why a fire spreads; can occur via three mechanisms: conduction, radiation, and convection

automobile paint--clearcoat

unpigments clearcoat to improve gloss, durability, and appearance; acrylic or polyurethane based

restriction fragment length polymorphisms (RFLP)

until mid-1990's, the forensic community focused its efforts on characterizing repeated DNA segments known as this; they used restriction enzymes to cut repeats out of DNA; these will be different sizes for different people and can be used for DNA profiling

high-velocity spatter

usually greater than 30 m/s (>100 ft/s); small droplets (<1 mm) and often has a mist-like appearance; usually from bullets, but can also be from sneezing

fabric impressions

usually identified as woven or knitted fabric; conclusions--"consistent with known source," "dissimilar to known source," "inconclusive comparison," "unsuitable impression;" positive identification is possible, but rare

medium-velocity spatter

velocity from 1.5 - 7.5 m/s (5 - 25 ft/s); drops from 1 - 3 mm in diameter; from blunt weapons or stabbing

Are Efforts being made to Individualize Human Hair?

we learned in Chapter 11 that forensic scientists routinely isolate and characterize individual variations of DNA; hair is a poor source of DNA; the hair shaft contains mtDNA, which isn't as unique (individuals maternally related will have same mtDNA); if the root is present or follicular tissue, then it can contain nuclear DNA for sequencing

What creates individuality in footwear and tires?

wear and damage provide individualizing characteristics that in combination with each other permit individualization of a shoe or tire; *wear* is the erosion of the outsole or tread area due to frictional and abrasive forces which occur between the outsole or tread area and the ground; when a shoe or tire is new, it is not destined to wear in any particular fashion; the way and extent of wear is due to many different factors

other bloodstain patterns--contact/transfer patterns

when an object with blood on it touches one that does not have blood on it, this produces a contact or transfer pattern; ex: fingerprints, handprints, footprints, footwear prints, tool prints, fabric prints

casting impressions

when shoe or tire marks are impressed into soft earth or snow at the crime scene, their preservation is best accomplished by photography and casting; often dental stone (form of gypsum) is widely recommended for making casts; tracks in snow are treated with a wax coating first

collection of biological evidence

whole sample is desirable if possible; blood stains can be sampled using a sterile swab lightly moistened with distilled water; samples need to be air dry and packaged in separate paper bags or boxes; clothing is collected even if there is no visible blood; substrate control samples are desirable but not always necessary for DNA typing

Trinitrotoluene (TNT)

widely used military explosive; not affected by water; quite stable; yellow or grey solid

David Berkowitz--"Son of Sam"

wrote strange letters to people about their dogs--was suspected of shooting the neighbor's dog; called people around him demons; letters finally convinced police to investigate him; arrested outside his house August 10, 1977; admitted that he was "Son of Sam"; also claimed to be a serial arsonist (~1500); claimed to have been part of a Satanic Cult--the case is still opened because of this; claimed that the neighbor's dog told him to kill; plead guilty and was sentenced to 365 year; became a born again Christian in prison--heavily involved in the prison ministry; refused parole hearings; model prisoner