Chapter 3 Crime Scene Investigation and Laboratory Analysis

Chapter 3: Crime Scene Investigation and Laboratory Analysis of Biological Evidence Forensic Biology by Richard Li

Forensic Investigations Involving Biological Evidence Requires: Crime scene examination ▪ Scene security, documentation, collection and preservation of evidence Laboratory analysis ▪ Utilizes scientific techniques for evidence examination, identification of biological fluids, and the comparison of individual characteristics Forensic Biology by Richard Li 2

Crime Scene Investigation Protecting and securing the scene: Duty of the first officer on the scene Only authorized personnel Use log sheet Obtain medical attention if needed Proper supplies and devices must be utilized ▪ E. g. Disposable suits, face mask, disposable gloves and booties Forensic Biology by Richard Li 3

Crime Scene Investigation Documentation Sketch ▪ Rough and Finished Photographs ▪ Use photo log sheet ▪ Use scale Video Forensic Biology by Richard Li 4

Crime Scene Investigation Chain of Custody- lists custody information at every point in time when evidence is handled or transferred Forensic Biology by Richard Li 5

Crime Scene Investigation Recognition of biological evidence ▪ Corpus delicti evidence ▪ Victim-to-perpetrator linkage evidence ▪ Victim-to-scene linkage evidence ▪ Perpetrator-to-scene linkage evidence ▪ Case-to-case linkage evidence ▪ Modus operandi Forensic Biology by Richard Li 6

Crime Scene Investigation Locard Exchange Principle: Cross-transference of evidence occurs when a perpetrator has any physical contact with something or someone else Scene Victim Perpetrator Forensic Biology by Richard Li 7

Crime Scene Investigation Searches Alternate Light Source (ALS) Types ▪ Spiral ▪ Grid ▪ Strip ▪ Quadrant/Zone Forensic Biology by Richard Li 8

Crime Scene Investigation Collection Only done after documentation is complete Consider collecting entire item if small enough or mobile Considerations ▪ ▪ ▪ Bloodstain pattern evidence Multiple analysis of evidence Trace evidence Control samples Size of the stain Wet Evidence Forensic Biology by Richard Li 9

Crime Scene Investigation Packaging and Transportation Goal: protect and preserve evidence Avoid heat and humidity Package items separately Allow wet items to air dry Use paper! Label properly and seal Forensic Biology by Richard Li 10

Laboratory Analysis Identification of biological evidence Comparison of individual characteristics of biological evidence Forensic Biology by Richard Li 11

Laboratory Analysis Class Characteristics Can be placed into a category with other similar materials Individual Characteristics Evidence possesses characteristics that share a common origin with a reference sample Forensic Biology by Richard Li 12

Laboratory Analysis Final steps: Reporting results Expert testimony Forensic Biology by Richard Li 13