Physical Evidence

Physical evidence: any object that can establish that a crime has been committed or link a crime or victim to a perpetrator

Evidence may consist of: witness testimony, records/documents, physical evidence (objects)

Common types of physical evidence: biological, chemical, trace, impression

Biological Evidence: forensic serology, forensic molecular biology

Questions for biological evidence: is it human? does it have sufficient DNA? whose is it?

Chemical Evidence: forensic chemistry/toxicology

Questions for chemical evidence: what is the substance? is there a foreign substance in bodily fluid? how much? is it similar to known standards?

Trace Evidence: forensic microscopy/geology/minerology

Questions for trace evidence: is this hair? is it human? what fiber is present?

Impression evidence: firearms, shoe prints, tool marks, tire treads, fingerprints, handwriting, bite marks

Questions for impression evidence: what type of weapon? did this weapon fire the bullet? what was the distance from the victim? did the suspect sign this document?

Impression evidence can be both 2D and 3D

Digital evidence: process of searching/analyzing digital devices for evidence of a crime (not comparison or identification technique)

Class Characteristics: comparison of item with another group of items, questioned evidence compared with known object to include or exclude

Comparisons: size, color, manufacturing pattern, chemical composition

Examples of class characteristics: hairs, fibers, soil, unknown powder or liquid, automotive paint

Individual Characteristics: can be contributed to an individual, identification

Identification: determination of identity of substance, object, person with near absolute scientific certainty

Examples of individual characteristics: fingerprints, nuclear DNA, firearms/toolmarks, footwear patterns, handwriting, broken/torn/cut edges