Forensic Science: An Introduction

1. Forensic Science: An Introduction Unit A: Crime Scene Processing

2. 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. • 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.

3. The American Academy of Forensic Science Departments • 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

4. Additional disciplines • Fingerprint examination • Firearm and toolmark examination • Computer and digital analysis • Photography • Entomology - insects

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

6. Publications • 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 1880s) • “Treaty of Criminalistics (Locard, 1931) • Hypervariable Minisatellite Regions in Human DNA (Jeffreys, 1985)

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

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

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

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

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

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

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

14. Ways to classify a crime scene • Primary vs secondary crime scene • Macroscopic vs microscopic scenes • Type of crime • Location of crime

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

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

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

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

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

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

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

22. Common Types of Evidence Blood, semen, and saliva Documents Drugs Fibers Fingerprints Firearms and ammunition Glass Hair Impressions Organs and physiological fluids 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 Common Types of Evidence

23. Examination of Physical Evidence • Identification • Determining the identity of a substance with a near absolute certainty while ruling out other substances • Comparison • 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)

24. Significance of Physical Evidence • Assessing the values of evidence • 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.

25. Forensic Databases • One-on-one comparison requires a suspect • Computerized databases help link evidence to people • Fingerprint databases – IAFIS • DNA database – CoDIS • Ballistics database – IBIS • Automative Paint database – PDQ • Shoeprint database - SICaR

26. 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 • Combined efforts of MEs, CSI, and law enforcement personnel • Examples: was body moved, bullet trajectory, blood splatter

27. History • 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

28. Fingerprint Principles • 1. A fingerprint is an individual characteristic; no two fingerprints have been found to possess identical ridge characteristics • No minimum number of comparisons to establish identity • 2. A fingerprint remains unchanged during an individual’s lifetime • 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.

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

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

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

32. Classification of Fingerprints • Henry system – numerical system involving the presence or absence of the whorl pattern on each finger as part of the primary classification.. • 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 • Data entered now by Livescan rather than ink rolling. • Human decisions must still be made • Software incompatibilities among states

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

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

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