Investigation into Stutter Ratio Variability Between Different Laboratories

• NCJ Number: 249325
• Author(s): Jo-Anne Bright, James M. Curran
• Date Published: November 2014
• Length: 3 pages
• Agencies: NIJ-Sponsored
• Award: Population Genetic Issues for Forensic DNA Profiles

Annotation

Since the determination of parameters such as stutter ratio is important to inform a laboratory's forensic DNA profile interpretation strategy, this article reports on the implementation of a continuous model of DNA profile interpretation that analyzed stutter ratio data from eight different forensic laboratories for the Promega PowerPlex® 21 multiplex, which enabled a comparison of inter-laboratory variation.

Abstract

This was done as part of a large data analysis project to implement a continuous model of DNA profile interpretation. The comparison of inter-laboratory stutter ratio data variation found that the maximum difference for any one laboratory from the average of the best fit determined by the model was 0.31 percent. These results indicate that stutter ratios calculated from samples analyzed using the same profiling kit are not expected to differ between laboratories, even those using different capillary electrophoresis platforms. A common set of laboratory parameters can be generated and used for profile interpretation at all laboratories using the same multiplex and cycle number, potentially reducing the need for individual laboratories to determine stutter ratios. (Publisher abstract modified)