NCJ Number
217114
Journal
International Journal of Forensic Identification Volume: 57 Issue: 1 Dated: January/February 2007 Pages: 19-31
Date Published
January 2007
Length
13 pages
Annotation
This study developed equations that determine the errors or uncertainties in the horizontal and vertical angles calculated for crime-scene bullet paths constructed with the trigonometric method.
Abstract
The proposed equations have been successfully applied in determining the uncertainty in the point of origin of a pair of blood drops. The equations developed are intended for use by crime-scene reconstructionists in their expert court testimony regarding errors or uncertainties in their calculations of both horizontal and vertical angles of bullet paths based on the location of bullet holes. The equations were derived from the use of the trigonometric method of determining bullet paths at a crime scene as an alternative to the use of the stringing method. In the trigonometric method, linear measurements are used to calculate the horizontal and vertical angles of the bullet's path. In the 1993 Daubert court decision, the U.S. Supreme Court presented criteria that Federal trial judges should use in evaluating the admissibility of scientific evidence. In the subsequent "Joiner" and "Kumho" Supreme Court decisions, the Court extended the application of criteria for admissibility to technical evidence generally. One of the criteria for admissibility of such evidence is the presentation of the known or potential error rate for the scientific technique used in developing the evidence presented. In the case of the trigonometric method for calculating bullet paths, the known or potential error in the horizontal and vertical angles of the bullet's path must be calculated from the errors or uncertainties in the linear measurements from which the angles are calculated. The equations presented in this paper provide this information. 7 figures and 9 references