unit 4 forensics

8/11/2019 Unit 4 Forensics

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8.1 Introduction to DNAFingerprinting and Forensics

Forensic science intersection of lawand scienceHistoric examples

1800s photographyEarly 1900s fingerprints

DNA Fingerprinting 1985Unique signature found in each personsgenetic makeup


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FingerprintingFingerprints have been used as a means ofidentification dating back well over two thousandyears. Over the past century, the fingerprintingprocess has become more sophisticated, and it

has been put to many more uses.The first documented fingerprints were taken inIndia in 1858 by Sir William J. Hershel.Soon thereafter advances were made on severalfronts, and Sir Edward Henry devised aclassification system around the turn of the 20thcentury that is still in practice today


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Types of FingerprintsThe three distinct types of fingerprints thatcan be recovered from a crime scene arepatent, plastic, and latent prints.The knowledge of the types of fingerprintshastens the investigator's quest to identifythe source of the fingerprints


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PATENT PRINTS - are visible prints thatoccur when a foreign substance on the skinof a finger comes in contact with the smoothsurface of another object .

These prints leave a distinct ridge impressionthat is visible with the naked eye withouttechnological enhancement of any kind.

The tried and true " blood on his hands "evidence is an example of patent printsrecovered from a crime scene or scene ofinterest to investigators.

These foreign substances contain dustparticles which adhere to the ridges of thefingers and are easily identifiable when left onan object.


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PLASTIC PRINTS - are visible, impressed printsthat occur when a finger touches a soft, malleable

surface resulting in an indentation .Some surfaces that may contain this typeof fingerprint are those that are freshlypainted or coated, or those that containwax, gum, blood or any other substancethat will soften when hand held and thenretain the finger ridge impressions.

These prints require no enhancement inorder to be viewed, because they areimpressed onto an object and are easilyobservable.


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LATENT PRINTS - are fingerprint impressions secreted ina surface or an object and are usually invisible to the nakedeye.

These prints are the result of perspiration which is derivedfrom sweat pores found in the ridges of fingers.

When fingers touch other body parts, moisture, oil andgrease adhere to the ridges so that when the fingers touch

an object, such as a lamp, a film of these substances maybe transferred to that object.

The impression left on the object leaves a distinct outlineof the ridges of that finger.

These fingerprints must be enhanced upon collection and,because they serve as a means of identifying the sourceof the print, they have proven to be extremely valuableover the years in the identification of its source.


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Fingerprint Classification

Fingerprint classification was developed by SirFrancis Galton in 1888 so that fingerprints couldbe retrieved in a reasonable amount of time.

Sir Edward Henry expanded on Galton'ssystem, and his manual filing system paved theway for the computerized classification systemsthat exist today.


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The patterns of the ridges of our fingers are distinct in everyindividual.The four basic pattern classifications established by SirEdward Richard Henry in 1896 are

the arch, the loop, the whorls, and the composites(loops).

Even to this day, Sir Henry's work on fingerprint patternshas held up under critical review.


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Fingerprint Criticism The human element eliminates the infallibility of the fingerprint methodology as apersonal identification mechanism. Mistakes can be made by the administrator in theprocess of printing, or by the expert who is responsible for making the finaldetermination upon review of the possible matches.There is no data available that could quantify the percentage of errors made in

personal identification through the utilization of fingerprints.There are also errors that can occur in the process of taking inked fingerprints. Thefingerprints can be rendered illegible in the inking process if:

The finger has not been rolled fully from side to side.The entire finger from its joint to its top has not been inked.The finger is not held securely in place. If the technician holds the fingers too loosely (ortoo securely), there could be a smudging or blurring of the prints, thus rendering a falsepattern of prints.The usage of an inappropriate texture of ink can result in running of the ink and patterndistortion. Black printer's ink of a heavy texture is the advisable texture to use.The usage of too much ink can distort the patterns.The usage of too little ink will render the ridge patterns indistinguishable.Temporary disabilities to the fingerprint subject, such as cuts and blisters, can distort thepattern of the ridges.

Excessive perspiration on the fingers of the subject may inhibit the ink from adhering to thefingers which would result in a blurred and inaccurate outcome.Errors made on the information card that accompanies the fingerprints, such asname, date of birth, sex and age can lead to complications as to the authenticity ofthe prints.


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Defense Fingerprints are the ultimate source in the establishment of both the verificationand recognition of a person's identity. This statement is based on three factors:fingerprints are distinct and unique to each individual, and no two people haveidentical prints; fingerprints are unchangeable over the course of a lifetime of a

person; and fingerprints can be extracted from any surface they come into contactwith.InexpensiveReliableFast ResultsMulti-faceted usage, including criminal, commercial, financial and civilianidentificationsDeterrent to crime and fraudEffective in streamlining business processesPreservation of personnel and financial resources in both the private and publicsectors. Fingerprinting is the most basic and assured of security mechanisms.World wide computerized system is already in effect and extremely valuableduring criminal investigations, since the database has been established.Identifies who a person is, as opposed to what a person has, such as a password,pin # or other identification of that nature. It establishes identification through theidentification of unchangeable personal characteristics. A person may change haircolor, but cannot alter fingerprints. One cannot guess, fake or forget fingerprints ascan occur in non-biometric identification methodologies. The individual who isfingerprinted must be physically present in order to be processed.


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8.2 What Is a DNA Fingerprint?

Every individual carries a unique set ofgenes

Chemical structure of DNA is same, but theorder of the base pairs differs

Every cell contains a complete set of DNAthat identifies the organism as a whole

Only one tenth of 1% of DNA differs fromperson to person


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Two Main Types of Forensic DNA TestingRFLP (restriction fragment length polymorphism)

Requires larger amounts of DNADNA cannot be degradedRFLP

was one of the first applications of DNA analysis to forensicinvestigation. With the development of newer, more efficientDNA-analysis techniques, RFLP is not used as much as it oncewas because it requires relatively large amounts of DNA. Inaddition, samples degraded by environmental factors, such as

dirt or mold, do not work well with RFLP.Log onto: http://www.pbs.org/wgbh/nova/sheppard/analyze.html

PCR (polymerase chain reaction)Less DNA and DNA can be partially degraded

Extremely sensitive to contaminating DNA
http://www.pbs.org/wgbh/nova/sheppard/analyze.htmlhttp://www.pbs.org/wgbh/nova/sheppard/analyze.html


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Lets try a virtual DNA fingerprint lab!

Want to see the evidence from the OJ case? http://www.law.umkc.edu/faculty/projects/ftrials/Simpson/simpson.htm

Click on incriminating evidenceThen DNA evidence (on the top in the center)
http://www.law.umkc.edu/faculty/projects/ftrials/Simpson/simpson.htmhttp://www.law.umkc.edu/faculty/projects/ftrials/Simpson/simpson.htm


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DNA profiling depends on a smallportion of the genome

Exons code proteins (proteins that are expressed)

These are the 99.9% that makes us similarIntrons do not code for proteins (these are what makeus different)

The introns contain repeated sequences of between1 and 100 base pairsCalled variable number tandem repeats (VNTRs)

Some VNTRs are inherited from mother andsome from father


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DNA fingerprinting is restricted to thedetection of microsatellites

1 to 6 nucleotide repeats dispersed throughoutthe chromosomesProbes used to identify the microsatellitesurround the specific microsatellite being

analyzed Also called short tandem repeats (STR)FBI has chosen 13 unique STRs for testing

Combined DNA Index System (CODIS)


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8.3 Preparing a DNA Fingerprint

Specimen CollectionSearch for sources of DNACollection requires scrupulous attention todetail

Wear disposable gloves; change them frequentlyUse disposable instruments

Avoid talking, sneezing, and coughing

Avoid touching any item that might contain DNA(face, nose, or mouth) Air-dry evidence before packaging; mold cancontaminate a sample


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8.3 Preparing a DNA FingerprintEnemies of Evidence

Sunlight and high temperatureBacteriaMoisture

DNA fingerprinting is a comparative processSamples from crime scene must be compared to suspectDNABest sample from suspect DNA is fresh, whole blood

Extraction of DNADNA can be purified

Chemically (using detergents)Mechanically (pressure to force DNA out of cell)


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RFLP Analysis: Restriction FragmentLength Polymorphism

Treat DNA with restriction enzymeRestriction enzyme cuts DNA at restriction sitesUse several restriction enzymes in sequence orcombined

Use agarose gel electrophoresis to separatethe piecesGel is chemically treated or heated to denaturethe DNA

Allows the binding of a single-stranded probe


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Southern Blot TechniqueTransfer DNA fragments from gel to nitrocellulose ornylon membrane

Membrane incubated with a probeShort strand of complementary DNA with a radioactive orfluorescent tagTargeted area on the DNA fragment is called a locus

Expose X-ray (photo) film to membrane to obtainpermanent record of results


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PCR used to amplify DNA found at crimescene into an amount that can be analyzedDNA produced is identical to the originalsampleUse amplified DNA in a Dot Blot Analysis

DNA amplified by PCR is blotted onto speciallyprepared blot strips

Each dot on the strip is a different DNA probe from humanDNA

Try a virtual one for yourself!

http://www.wiley.com/college/boyer/0470003790/animations/animations.htm

http://learn.genetics.utah.edu/content/labs/pcr/
http://www.wiley.com/college/boyer/0470003790/animations/animations.htmhttp://learn.genetics.utah.edu/content/labs/pcr/http://learn.genetics.utah.edu/content/labs/pcr/http://www.wiley.com/college/boyer/0470003790/animations/animations.htm


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STR AnalysisSTR: Small Tandem Repeats

Use primers to amplify STRs in DNA usingPCRFBI uses 13 STR regions

Odds that two individuals will have thesame 13-loci DNA profile are more thanone in a billion

Check out the 13 loci profiles that get loaded into CODIS(the FBIs DNA Database!)

http://www.cstl.nist.gov/strbase/fbicore.htm
http://www.cstl.nist.gov/strbase/fbicore.htmhttp://www.cstl.nist.gov/strbase/fbicore.htm


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8.4 Putting DNA to UseDNA fingerprinting is a comparativeprocess

Looking for alignment of bands or dots in thefingerprint

All tests are based on exclusionTesting continues only until a difference is foundIf no difference is found after a statisticallyacceptable amount of testing, the probability of amatch is high


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Narborough Village Murders1983 first reported use of genetic fingerprinting ina criminal caseSexual assault and murder of girl in UnitedKingdom

The prime suspects DNA did not match that foundat crime scenePolice collected 5500 samples from the areaspopulation of likely suspectsNone of the DNA profiles matched the crime sceneFriend of suspect had given a sample in the nameof the suspect


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Forest Hills RapistDNA first used in United States 1987Victor Lopez tried for the sexual assault ofthree women

Reported assailant was a black man; Lopez was not

a black manDNA was a match to crime scene


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Terrorism and Natural Disasters

They have forced development of newtechnologies

World Trade Center September 11, 2001

Used DNA techniques to identify the remains ofvictimsTremendous amount of debris, heat, and microbialdecomposition of remainsHundreds of thousands of tissue samples fromnearly 3,000 individuals


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World Trade Center

Evident that new strategies would benecessary to quickly prepare andorganize DNA profiles and compare themwith DNA profiles from relatives

Within 24 hours, collection points had beenestablished around the city

Family filed missing person reports and providedcheek cell swabs for DNA isolation; personalitems from the missing were also collected


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World Trade CenterSeveral companies were involved in

developing new software programs to helpmatch DNA samples from family members toDNA profiles of victimsUsed primarily STR, mtDNA, and SNPanalysis


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South Asian TsunamiDecember 2004Lost over 225,000 livesmtDNA (mitochondrial), Y- STRs (Y -DNA)Within 3 months, 800 victims had been identified


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8.5 DNA and the Rules of EvidenceDNA fingerprinting had to meet legalstandards regarding the admissibility ofevidence5 different standards used

Relevancy testThe Frye standardThe Coppolino standard

The Marx standardThe Daubert standard


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Simpson/Goldman MurdersCollected 45 samples for DNA analysis, including knownblood samples from the two victims and the suspect;blood drops found at the crime scene, in the suspectshome, and in his carPre-trial hearings announced that the DNA collected atthe crime scene matched that of O.J. SimpsonDefense lawyers attacked the procedures used incollecting, labeling, and testing the evidence

Possibility that evidence was tainted became obviousDNA evidence not effectiveWant to see more about the case?

http://investigation.discovery.com/videos/crimes-of-the-century-oj-simpson-videos/


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DNA in the News

Tsunami in JapanTornados in Alabama and across theMidwestOsama Bin Ladden Identification


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Human Error and Sources ofContamination

Chain of custody of samples is compromisedCollection of evidence must be systematicallyrecorded and access to evidence must be controlled

Follow defined standards of laboratory practiceand procedures to prevent DNA damageduring the analysis

DNA and JuriesMust make sense to the juryStatistics can be confusing


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8.6 Familial Relationships and DNA ProfilesPaternity Testing

Analyze samples from child and adults involvedMitochondrial DNA

Used to examine samples that cannot be analyzed byPCR or RFLP

Older samples that lack nucleated cellular material(hair, bones, and teeth)

Inherited from the mother onlyChanges only about 1% every million years due torandom mutation

http://findarticles.com/p/articles/mi_m2194/is_8_71/ai_90819640/pg_5/ Check out some crimes that have been solved using mtDNA!
http://findarticles.com/p/articles/mi_m2194/is_8_71/ai_90819640/pg_5/http://findarticles.com/p/articles/mi_m2194/is_8_71/ai_90819640/pg_5/


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Y-Chromosome AnalysisPassed directly from father to son

Useful for tracing relationships among males oranalyzing biological evidence involving multiplemale contributors

Wanna try some DNA Heritage investigating?(it will only $159 )

http://www.dnaheritage.com/mtdna.asp
http://www.dnaheritage.com/mtdna.asphttp://www.dnaheritage.com/mtdna.asp


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8.7 Nonhuman DNA AnalysisGinseng

$3 million market in U.S. aloneTwo major herbal products are referred to asginseng

One native to North America, the other native to Asia Asian ginseng boosts energy; American ginsengcalms nerves

American variety is rarer and more valuable


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Prove a hunter killed a bear illegally in PA A law makes it illegal to kill a bear in a den

Witness reported seeing a hunter discharge guninto denBears premolars were removed at registrationstation to confirm sex and age of bearCollected blood samples from the den andcompared with DNA from bear; were a match

DNA Tagging to Fight Fraud

Use DNA as an authentication label hidden in awide variety of productsFootballs in 2003 Super Bowl2000 Sydney Summer Olympics


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Ancestry of Cabernet SauvignonGrapes

Hybrid grapes are considered inferior andare legally excluded from bearing theprestigious dinstinction appellation doriginecontrle in FranceDNA evidence determined that theancestors of cabernet sauvignon grapes are

cabernet franc and sauvignon blanc


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unit 4 forensics

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