NCJ Number
95704
Date Published
1984
Length
260 pages
Annotation
Describes the various uses of physical evidence in criminal investigations and the effects of such evidence on the solution of crimes and on the apprehension and prosecution of offenders. The study was based on 1,600 investigations in which physical evidence was collected and examined and on 1,100 cases where physical evidence was not used. Data were collected in four Peoria, Ill,; Chicago, Ill.; Kansas City, Mo.; and Oakland, Calif. Data collection spanned an 18-month period from September 1980 to February 1982.
Abstract
The authors explain the process that controls the recognition, collection, and examination of physical evidence and describe evidence from the 1,600 sample cases. They identify the most frequently collected types of evidence and discuss variables (such as the time lapse between discovery of the crime and its report to the police) that affect evidence gathering. Characteristics of criminal incidents that help to explain the types and quantities of evidence collected are discussed, and rates of clearance, charging, and conviction are compared in the presence of absence of physical evidence. Evidence is shown to have a substantial effect on robberies (when there are no witnesses and no suspects) and burglaries (when a witness is located, but there are no suspects), but a negligible effect on assaults. Policy recommendations for police agencies are provided.