NCJ Number
218822
Date Published
July 2000
Length
5 pages
Annotation
The Scientific Working Group on DNA Analysis Methods (SWGDAM) presents a framework for a forensic laboratory to develop short tandem repeat (STR) interpretation guidelines.
Abstract
A laboratory's STR interpretation guidelines should be based on validation studies, data from the literature, instrumentation used, and/or casework experience. For the preliminary evaluation of data, the laboratory should develop criteria for determining whether the results are of sufficient intensity/quality for interpretation purposes by using methods appropriate for the detection platform. These criteria should be determined by evaluating data generated by the laboratory. The laboratory should also develop criteria for evaluating internal lane size standards and/or allelic ladders. Controls are required for assessing analytical procedures. A laboratory that uses STR multiplexes that contain redundant loci should establish criteria for the concordance of such data. Regarding designation, the laboratory should establish criteria for assigning allele designation to appropriate peaks or bands. Artifacts (phenomena that do not accurately show the sample's characteristics) can occur and should be noted. Guidelines based on empirical data should be established in order to address the interpretation of various artifacts. Regarding the interpretation of results, the laboratory should define conditions in which the data would lead to the conclusion that the source of the DNA is either from a single person or more than one person. In addition, the laboratory should have guidelines for the interpretation of partial profiles (profiles with fewer loci than tested) that may arise from degraded or limited quantity DNA or from the presence of polymerase chain reaction (PCR) inhibitors. Further, guidelines should be developed for interpreting profiles that show potential stochastic effects (e.g., allele dropout and/or substantial imbalance of alleles). SWGDAM recommendations also address guidelines for conclusions and statistical interpretation. 5 references