Validation and casework application of a Y chromosome specific STR multiplex

A series of validation experiments was performed for a Y chromosome specifi c STR multiplex system following the suggestions made by the Technical Work ing Group DNA Analysis Methods (TWGDAM). The multiplex PCR products were de tected on Perkin-Elmer 373 and 377 automated sequencers using two labeling colors. No problems regarding the stability, robustness and sensitivity of the Y STR multiplex were observed. Mixture studies revealed a cut off rate similar to autosomal STRs for mixtures of male DNAs and no interference of any female admixture. The comparison of the Y STR results to the autosomal typing results for 56 nonprobative semen stains and swabs, showed a slightl y higher Success rate in detecting the semen donor's alleles for the Y STR multiplex. Two examples are shown to illustrate the usefulness of Y STR typ ing for DNA mixtures. In one case the Y STIR results confirmed an isolated exclusion; in the other case, the interpretation of a mixture was clarified since the Y STR results proved the presence of DNA from at least two semen donors. Y STR typing is a valuable addition to the forensic DNA testing pa nel. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.