NCJ Number
141997
Journal
Judicature Volume: 76 Issue: 5 Dated: (February-March 1993) Pages: 222-230
Date Published
1993
Length
9 pages
Annotation
Since its introduction in 1987, DNA fingerprinting has been used to convict over 1,000 criminal and civil defendants. Once seen as a foolproof way to identify criminals who left blood and body fluid samples at the crime scene, there is now an awareness that DNA analyses are subject to error and may be misinterpreted.
Abstract
DNA typing produces a pattern called a DNA profile. If the bands in the profile line up with those in the trace evidence, within a specified margin of error, there is a match. While DNA matching evidence is probative, a match only estimates the probability that a defendant is the source of the sample. DNA samples are often used in paternity cases, but the analysis cannot tell the likelihood that an alleged father is the true father of a particular child. Laboratories may claim a 50 percent prior probability assumption, but that is misleading and could be prejudicial to the defendant. Furthermore, probability estimates made by laboratories do not allow for genetic similarities in source or suspect populations. The two major categories of error in DNA fingerprinting include false positives and false negatives. This author argues that laboratories should be required to provide conservatively high estimates of their false positive error rates when providing genetic matches, as well as information on false negative error rates when reporting an exclusion. 1 figure and 24 notes