Forensic Science An Introduction Unit A Crime Scene

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Forensic Science: An Introduction Unit A: Crime Scene Processing

Forensic Science: An Introduction Unit A: Crime Scene Processing

Definitions Forensic Science - the application of the knowledge and technology of science to

Definitions Forensic Science - the application of the knowledge and technology of science to the criminal and civil laws that are enforced by police agencies in a criminal justice system. l Locard’s Exchange Principle – when two objects come in contact with each other, a cross-transfer of materials occur. This allows us to connect criminals to crime scenes. l

The American Academy of Forensic Science Departments l l l l l Criminalistics -

The American Academy of Forensic Science Departments l l l l l Criminalistics - crime scene processing Engineering Science - reconstruction General Jurisprudence - legal Odontology - bitemarks Pathology/Biology – autopsy, DNA Physical Anthropology – skeletal remains Psychiatry and Behavioral Science Questioned Documents Toxicology – drugs and poisons

Additional disciplines Fingerprint examination l Firearm and toolmark examination l Computer and digital analysis

Additional disciplines Fingerprint examination l Firearm and toolmark examination l Computer and digital analysis l Photography l Entomology - insects l

Historical Events Late 1700 s - Arsenic and Toxicology l Mid 1800 s –

Historical Events Late 1700 s - Arsenic and Toxicology l Mid 1800 s – Microscopy l Late 1800 s – Identification (Bertillion) l Early 1900 s – Fingerprinting, Blood and Serology, Document Examination, Microscopy l Mid 1900 s – Chromatography, Spectrophotometry, Electrophoresis, DNA l

Publications l l l l Yi Yu Ji “A Collection of Criminal Cases” “A

Publications l l l l Yi Yu Ji “A Collection of Criminal Cases” “A Treatise on Forensic Medicine and Public Health” (Fodere, 1798) “Finger Prints” (Galton, 1892) “Criminal Investigation” (Gross, 1893) Sherlock Holmes –fiction (Doyle 1880 s) “Treaty of Criminalistics (Locard, 1931) Hypervariable Minisatellite Regions in Human DNA (Jeffreys, 1985)

Crime Labs l l l l l Locard Los Angeles - oldest FBI DEA

Crime Labs l l l l l Locard Los Angeles - oldest FBI DEA ATF US Postal Service SBI State system Local Delocalized labs – no common management

Crime Lab Services Basic Services l Photography l Physical Science l Biology/DNA l Firearms

Crime Lab Services Basic Services l Photography l Physical Science l Biology/DNA l Firearms l Document Examination Optional Services l Toxicology l Latent Fingerprint l Polygraphy l Voice Analysis l l Forensic Psychiatry Forensic Odontology Forensic Engineering Forensic Computer and Digital Analysis

What Forensic Scientists Do l Analyze physical evidence l Use l Determine admissibility of

What Forensic Scientists Do l Analyze physical evidence l Use l Determine admissibility of evidence l Frye l scientific methods v US (1923) – general acceptance Judge scientific evidence l Daubert case (1993) – trial judge is gatekeeper Provide expert testimony l Furnish training l

Forensic Science Forensic scientist seek to reach truth based on available evidence. The legal

Forensic Science Forensic scientist seek to reach truth based on available evidence. The legal process does not, however, always seek truth but follow process. l Reliable methods possess characteristics of: l l Integrity l Competence l Defensible technique l Relevant experience

Reliable Methods Help distinguish evidence from coincidence l Allow alternative results to be ranked

Reliable Methods Help distinguish evidence from coincidence l Allow alternative results to be ranked by basic scientific principles l Allow tests to either prove or disprove alternative hypotheses l Pursue testing by breaking hypotheses into their smallest logical components l

Physical Evidence Anything physical objects that can link a crime to its victims or

Physical Evidence Anything physical objects that can link a crime to its victims or to suspects. l Has to be collected from crime scene l Must be relevant to the crime l Requires the collector to understand what the capabilities and limitations of the crime lab are l

Physical Evidence Crime labs do not solve crimes, only add evidence to help police

Physical Evidence Crime labs do not solve crimes, only add evidence to help police investigation link the suspect to the crime. l The forensic scientists must know how to collect and preserve evidence found at the crime scene l

Ways to classify a crime scene Primary vs secondary crime scene l Macroscopic vs

Ways to classify a crime scene Primary vs secondary crime scene l Macroscopic vs microscopic scenes l Type of crime l Location of crime l

Use of Physical Evidence Information on evidence of a crime (Corpus Delecti) l Information

Use of Physical Evidence Information on evidence of a crime (Corpus Delecti) l Information on the criminal (Modus Operandi) l Linkage on persons, scenes and objects l Identification of suspects l Identification of unknown substances l Reconstruction of a crime l Providing investigative leads l

Arriving at the Crime Scene Secure and isolate the crime scene l Determine boundaries

Arriving at the Crime Scene Secure and isolate the crime scene l Determine boundaries of crime scene and priorities for evidence collection l Rough sketch l Finished sketch l Photograph l Videotaping l Notes l

Collecting Evidence Conduct a systematic search for evidence; be unabiased and thorough. l Field

Collecting Evidence Conduct a systematic search for evidence; be unabiased and thorough. l Field technicians l What to look for depends on the crime and what specific locations of the crime scene would most likely be affected l Microscopic or massive objects l Collect carriers of possible evidence l Vacuum or sweeping collected l

Packaging of Evidence Prevent any changes from occurring (contamination, breakage, evaporation, bending, loss) l

Packaging of Evidence Prevent any changes from occurring (contamination, breakage, evaporation, bending, loss) l Process trace evidence from original object (shirt, shoe) rather than isolating and packaging if possible l Package evidence separately l

Tools for Collecting Evidence Forceps l Evidence envelopes and pill bottles l Swabs l

Tools for Collecting Evidence Forceps l Evidence envelopes and pill bottles l Swabs l Special concerns (mold, evaporation) l Various light sources l Latent fingerprints l Mobile crime labs or better yet crime scene search vehicle l

Chain of custody Continuity of possession; every person who touched it must be accounted

Chain of custody Continuity of possession; every person who touched it must be accounted for l Standards for collecting, labeling, and submitting evidence forms are necessary for court l Labels include collectors initials, location of evidence, date of collection. Identification numbers must also be used l

Submission of Evidence Standard/reference samples l Substance controls l Evidence submission form will detail

Submission of Evidence Standard/reference samples l Substance controls l Evidence submission form will detail the evidence collect and particular type of examination/analysis requested. l Lab tech not bound by requests l

Common Types of Evidence l l l Common Types of Evidence Blood, semen, and

Common Types of Evidence l l l Common Types of Evidence Blood, semen, and saliva Documents Drugs Fibers Fingerprints Firearms and ammunition Glass Hair Impressions Organs and physiological fluids l l l l l Paint Petroleum products Plastic bags Plastic, rubber, and other polymers Powder residues Serial numbers Soil and minerals Tool marks Vehicle lights Wood and other vegetative matter

Examination of Physical Evidence l Identification l l Determining the identity of a substance

Examination of Physical Evidence l Identification l l Determining the identity of a substance with a near absolute certainty while ruling out other substances Comparison l l l Comparing the evidence to one or more selected references and drawing a conclusion about its origins. Individual characteristics –properties of evidence that can be attributed to a common source with extremely high certainty. (eg. fingerprints, DNA, bullets) Class characteristics – properties of evidence that can be associated with a group and never with a single source. ( eg. Blood type, tire marks)

Significance of Physical Evidence l Assessing the values of evidence l l Class characteristics

Significance of Physical Evidence l Assessing the values of evidence l l Class characteristics of evidence is valuable in corroborating events. Multiple class evidence can lead to a high level of certainty of origin Cautions and limitations of evidence A person can be exonerated or excluded from suspicion if evidence collected from the crime scene is different from the reference samples collected from the person.

Forensic Databases l l l l One-on-one comparison requires a suspect Computerized databases help

Forensic Databases l l l l One-on-one comparison requires a suspect Computerized databases help link evidence to people Fingerprint databases – IAFIS DNA database – Co. DIS Ballistics database – IBIS Automative Paint database – PDQ Shoeprint database - SICa. R

Crime-Scene Reconstruction The method used to support a likely sequence of events at a

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 those involved with the incident l Combined efforts of MEs, CSI, and law enforcement personnel l Examples: was body moved, bullet trajectory, blood splatter l

History l l l Alphonse Bertillion (1883) – anthropometry Henry Fauld (1880) - first

History l l l Alphonse Bertillion (1883) – anthropometry Henry Fauld (1880) - first published on possible use of fingerprints Francis Galton (1892) – published Finger Prints described types of prints Sir Edward Henry (1897) – classification system used today FBI (1924) – new formed FBI held world’s largest fingerprint database

Fingerprint Principles l 1. A fingerprint is an individual characteristic; no two fingerprints have

Fingerprint Principles l 1. A fingerprint is an individual characteristic; no two fingerprints have been found to possess identical ridge characteristics l l 2. A fingerprint remains unchanged during an individual’s lifetime l l No minimum number of comparisons to establish identity Friction ridges and grooves created by dermal papillae Sweat glands on the ridges deposit perspiration and oils Latent fingerprint – left by deposits and is invisible to the naked eye 3. Fingerprints have general ridge patterns that permit them to be systematically classified.

Categories of Fingerprints l Loop – ridge lines enter one side of pattern and

Categories of Fingerprints l Loop – ridge lines enter one side of pattern and curve around to exit from the same side of pattern. (65%) l Ulnar loop – opens toward little finger l Radial loop – opens toward thumb Ulnar Loop Radial Loop

Categories of Fingerprints l Whorl – ridge lines rounded or circular and have two

Categories of Fingerprints l Whorl – ridge lines rounded or circular and have two deltas(30 -35%) l Plain whorl l Central pocket loop l Double loop l Accidental loop

Categories of Fingerprints l Arch – ridge lines enter print from one side and

Categories of Fingerprints l Arch – ridge lines enter print from one side and exit from the other (5%) l Plain l Tented

Classification of Fingerprints l Henry system – numerical system involving the presence or absence

Classification of Fingerprints l Henry system – numerical system involving the presence or absence of the whorl pattern on each finger as part of the primary classification. . l l This does not identify someone, only reduce the number of possible candidates AFIS – 10 print system that can search 500, 000 stored ten-prints in 0. 8 seconds l l l Data entered now by Livescan rather than ink rolling. Human decisions must still be made Software incompatibilities among states

Methods of Detection l Types of prints l Latent print l Visible print –

Methods of Detection l Types of prints l Latent print l Visible print – deposited ink, blood, dirt l Plastic print – impression in a soft surface l Locating prints – RUVIS

Developing Prints l Powders l Charcoal l Magnetic l Fluorescent l Chemicals l Iodine

Developing Prints l Powders l Charcoal l Magnetic l Fluorescent l Chemicals l Iodine fuming (sublimation) l Ninhydrin l Physical developer (silver nitrate) l Super Glue fuming l Alternate Light Sources/ LED

Preservation of Developed Prints Photographs l Print surface should be removed in its entirety

Preservation of Developed Prints Photographs l Print surface should be removed in its entirety (covered with cellophane) l Lifted from surface with tape l Digital imaging into pixels – allows adjustments to be made to enhance picture l