Physical Evidence

1. Physical Evidence bsapp.com

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

3. Purpose of Examining Physical Evidence • Identification or comparison purposes. PHYSICAL EVIDENCE

4. Common Types of Identification • Chemical composition of an illicit drug • Gasoline in residues recovered from the debris of a fire • Nature of explosive residues – for example, dynamite or TNT. • Blood, semen, hair, or wood are also very common and, as a matter of routine, include a determination for species origin. PHYSICAL EVIDENCE

5. The Role of Physical Evidence • Physical evidence left behind at a crime scene plays crucial role in reconstructing the events that took place • can support or contradict accounts given by witnesses and/or suspects • generate leads and confirm the reconstruction of a crime to a jury • The collection and documentation of physical evidence is the foundation of a reconstruction. PHYSICAL EVIDENCE

6. Types of Analysis Comparison Visual Microscopic Chemical bsapp.com

7. Almost all evidence requires one or more types of analysis • Types of Analysis • Comparison – fingerprints, hairs • Visual – fingerprints, tool marks • Microscopic – hairs, fibers • Chemical – paint chips, DNA, drug screening

8. Comparison Most types of evidence require a control with which to be compared bsapp.com

9. Visual Analysis Evidence utilized through unaided observation bsapp.com

10. Microscopic Analysis Evidence observed with the use of some type of microscope bsapp.com

11. Chemical Analysis Evidence subjected to any type of chemical procedure bsapp.com

12. Accepted Forensic Databases • TheIntegrated Automated Fingerprint Identification System (IAFIS), a national fingerprint and criminal history system maintained by the FBI. • TheCombined DNA Index System (CODIS) enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles. • The National Integrated Ballistics Information Network (NIBIN) allows firearm analysts to acquire, digitize, and compare markings made by a firearm on bullets and cartridge casings. • The International Forensic Automotive Paint Data Query (PDQ) database contains chemical and color information pertaining to original automotive paints. • SICAR (shoeprint image capture and retrieval) is a shoeprint database. PHYSICAL EVIDENCE

13. Reconstruction of a crime scene

14. Figure 3–9  Crime-scene reconstruction relies on the combined efforts of medical examiners, criminalists, and law enforcement personnel to recover physical evidence and to sort out the events surrounding the occurrence of a crime.

15. Reconstruction • Reconstruction • method used to support a likely sequence of events by the observation and evaluation of physical evidence, as well as statements made by those involved with the incident PHYSICAL EVIDENCE

16. Figure 3–8  A laser beam is used to determine the search area for the position of a shooter who has fired a bullet through a window and wounded a victim. The bullet path is determined by lining up the victim’s bullet wound with the bullet hole present in the glass pane.