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)

what does physical evidence do

assist the jury or judge (the triar of fact)

Common types of physical evidence

biological, chemical, trace, impression

Biological Evidence

forensic serology, forensic molecular biology

Questions for biological evidence

what is the nature of the stain? 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 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? was it this one? did the suspect sign this document?

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

class v. individual characteristics for a bullt

class: 9mm, 6 lands and grooves with left twist; individual: striations