Presentation on theme: "Chapter 3 Physical Evidence Part II Naturally shed hairs, such as a head hair dislodged through combing, display undamaged, club-shaped roots Forcibly."— Presentation transcript:
Chapter 3 Physical Evidence Part II Naturally shed hairs, such as a head hair dislodged through combing, display undamaged, club-shaped roots Forcibly removed hairs may have tissue attached, damaged roots or exhibit stretching
Chain of Custody Revisited What is chain of custody? The record of everything that happened to the evidence from the moment it is discovered until it arrives in court or is destroyed after the final dispensation of the case. Proper ID and Labeling Paper trial for evidence transfer including signature, time, date, location Bar code systems
Why is Chain of Custody Important? Loss prevention Provides proof that evidence presented in court was collected from the crime scene and not altered or mishandled DNA Figure 1: Properly Stained Buccal Swab (left); Poorly Stained Buccal Swab (right)
Stages in the Analysis of Physical Evidence Recognition Identification Take measurements and analyze physical, chemical and biological properties to determine class characteristics Comparison Individualization Evidence is shown to be derived from a unique source Reconstruction Likely sequence of events of an incident as supported by physical evidence and testimony of witnesses
Forensic Databases Fingerprint Databases Integrated Automated Fingerprint Identification System (IAFIS) launched in 1999 maintained by FBI includes nearly 50 million subjects Forensic Brief p. 90 Saferstein, Forensic Science An Introduction
Forensic Databases DNA Databases Combined DNA Index System (CODIS) Fully operational in 1998 through FBI Data bank linked to all 50 states Sources include the offender index (3 million profiles of convicted or arrested individuals) and the forensic index (110,000 profiles from unsolved crime scene evidence) Forensic Brief, p. 91 Saferstein, FS An Intro
Other Databases National Integrated Ballistics Information Network (NIBIN) Maintained by Bureau of Alcohol, Tobacco, Firearms and Explosives Integrated Ballistic Identification System is a microscope and computer that captures an image of a bullet or cartridge casing, forwards to a server. IBIS does not positively match bullets or casings but produces a short list of candidates for firearms examiner to compare.
Other Databases International Forensic Automotive Paint Data Query (PDQ) Contains chemical and color information pertaining to original automotive paints Developed and maintained by Laboratory Services of the Royal Canadian Mounted Police Includes Ontario, Quebec, 40 US States, 21 other countries Accredited users must submit 60 new paint samples to the database each year Useful in hit & run investigations
Other Databases Shoeprint Image Capture and Retrieval (SICAR) Commercially available computer retrieval system for comparing and identifying crime- scene shoe prints Not maintained or controlled by a government agency Shoeprint images are scanned or digital pictures are entered. Database includes > 300 shoe manufacturers with > 8000 different sole patterns
Crime-Scene Reconstruction Likely sequence of events of an incident as supported by physical evidence and testimony of witnesses Determining bullet trajectory (See p. 73 Figure 3-4 Use of a laser beam to plot the approximate bullet path in trajectory analysis to determine the probable position of the shooter.) Analyzing Blood spatter patterns Determining direction of projectiles penetrating glass objects Locating gunshot residues deposited on victims clothing Searching for primer residues deposited on the hands of a suspect shooter
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