Criminal Investigation A Method for Reconstructing the Past

Criminal Investigation: A Method for Reconstructing the Past, 7 th Edition Book Cover Here Chapter 2 PHYSICAL EVIDENCE Development, Interpretation, Investigative Value Copyright © 2014, Elsevier Inc. All Rights Reserved 1

Forensic Science • The word forensic is derived from the Latin forensis, meaning “forum” • At least two major branches of forensic science are recognized – Criminalistics – Forensic Medicine Copyright © 2014, Elsevier Inc. All Rights Reserved 2

Forensic Science • Criminalistics – Drug Analysis/Toxicology – Firearms and Toolmarks – Photography – Trace, Implant, and Digital Evidence – Instrumental Chemistry, Forensic Biology/DNA – Crime Scene Reconstruction • Forensic Medicine – Anthropology and Psychiatry – Serology and Toxicology – Odontology Copyright © 2014, Elsevier Inc. All Rights Reserved 3

Criminalistics • The Development and Interpretation of Physical Evidence – Report of the National Academy of Sciences • Basic Concepts: Details in Physical Evidence – What are they? • Morphology (structure & form) – How are they developed? – Contrast • Optical and Analytical Instruments Copyright © 2014, Elsevier Inc. All Rights Reserved 4

Criminalistics • Basic Concepts – Identification – Identity • The Role of the Crime Laboratory • Reconstruction: Are the Facts Consistent with the Story? ? – Induce an Admission or Confession – Protect the Innocent – Provide Expert Testimony • The O. J. Simpson Case: The Sock Evidence Copyright © 2014, Elsevier Inc. All Rights Reserved 5

Forensic Medicine: Investigative Value • • Forensic Pathology Toxicology Forensic Odontology Forensic Psychiatry – Law Enforcement – The Courts – The Correctional System Copyright © 2014, Elsevier Inc. All Rights Reserved 6

Clue Materials as Information Sources • Fingerprints, Lip Prints, Ear Prints • Firearms • Semen, Other Biological Material, and DNA Profiling • Documents • Trace Evidence Copyright © 2014, Elsevier Inc. All Rights Reserved 7

Latent Fingerprints • Natural Sources • Environmental sources • Controlling Factors – Surface – Finger pressure Copyright © 2014, Elsevier Inc. All Rights Reserved 8

Fingerprint Evidence • Developing – Making Fingerprints Visible – Powders – Chemicals – Alternate Light Sources • Ultraviolet rays • Laser radiation • Preserving • Classifying & Identifying Copyright © 2014, Elsevier Inc. All Rights Reserved 9

Classifying & Identifying Fingerprints • Classification: Ridge Line Details – Patterns and class characteristics – Ridge Counting: Loops – Ridge Tracing: Whorls • Identification: Individualizations by Ridge Line Deviations – Identifying a Latent Print • Fingerprint Exemplars: Sources • Comparison of a Latent with a Known Fingerprint • Number of Points Necessary for an Identification Copyright © 2014, Elsevier Inc. All Rights Reserved 10

Fingerprint: Additional Considerations • Automated Fingerprint Identification Systems (AFISs) • Evidentiary Value – How Long Do Fingerprints Last? • Levels of Expertise • Probative Value Copyright © 2014, Elsevier Inc. All Rights Reserved 11

Firearms • Crime Scene Bullet or Cartridge & Suspected Weapon • Make and Mechanical Condition of Gun – Description and Operating Condition – Bullet Trajectory – Accidental Discharge – Trigger Pull • • • Restoration of Serial Numbers Shooting Distance Powder Traces on Gun Hand Weapon Recently Fired? – How Many Shots? Type and Model of Weapon Used Copyright © 2014, Elsevier Inc. All Rights Reserved 12

Blood • Investigative Uses – Locate the Crime Scene – Identify the Weapon or Instrument – Develop Associative Evidence – Reconstruct How the Crime was Committed – Corroborate or Disprove an Alibi – Interrogate a Suspect • Evidentiary Value Copyright © 2014, Elsevier Inc. All Rights Reserved 13

Semen, Other Biological Material, and DNA Profiling • DNA – What is it? • DNA – How is it analyzed? • Newer DNA Technology – Short Tandem Repeats (STRs) – Mitochondrial DNA • DNA – Investigative Use • DNA Results – Evidence and Proof Copyright © 2014, Elsevier Inc. All Rights Reserved 14

Documents • Handwriting and Hand-Printing Examinations • Typewriting and Computer Printing Examinations • Paper and Other Examinations Copyright © 2014, Elsevier Inc. All Rights Reserved 15

Glass and Trace Evidence • Glass – Direction of Break – Which Bullet Hole Was Made First? • Trace Evidence: very small physical evidence requiring special instruments in order to examine it – Fibrous substances – Particulate matter Copyright © 2014, Elsevier Inc. All Rights Reserved 16

Utility of Trace Evidence* 1. Reconstruct the event 2. Associate people, places, and things involved with the event 3. Surmise the occupations of the principals 4. Describe the environment or location involved in the event *Petraco (1986) Copyright © 2014, Elsevier Inc. All Rights Reserved 17

Conclusion • Most common clue materials – Fingerprints – Firearms evidence – Blood • Less common clue materials – Documents – Glass – Biological material • Trace evidence frequently overlooked Copyright © 2014, Elsevier Inc. All Rights Reserved 18