NCJ Number
222069
Journal
Forensic Science International: Genetics Volume: 2 Issue: 2 Dated: March 2008 Pages: 91-103
Date Published
March 2008
Length
13 pages
Annotation
This paper presents a new methodology in reporting complex DNA profiles using likelihood ratios; applying a low copy number (LCN) interpretation framework.
Abstract
The method described not only calculates the strength of evidence when the suspect is a contributor to the DNA profile, but it also calculates the strength of evidence when the suspect is not a contributor to the crime stain. There is no longer a need for an ‘inconclusive’ category for reporting purposes that is based on perceived complexity of the result. In principle, any profile, with any number of contributors, can be probabilistically evaluated against any set of hypotheses. The framework is provided to incorporate all alleles into the calculation without the need to specifically assign all of them to specific contributors or to stutter artifacts. This new method determines whether proposed improvements to models are effective or worthwhile. A number of different theories are brought together in order to devise a new protocol to interpret complex cases using likelihood ratios. The calculations are designed to be highly conservative and are widely applicable. A low copy number (LCN) interpretation framework is applied which includes the probabilities of dropout and contamination, to conventional DNA cases. By increasing the number of potential contributors to the DNA profile, the extra alleles that result can be accounted for. To accomplish this, a new kind of case-specific ‘Tippett’ test is applied. The method is easily extended to carry out ranked likelihood ration searches for suspects in national DNA databases. Tables, figures, appendix A, and references