THE VALIDATION OF A 7-LOCUS MULTIPLEX STR TEST FOR USE IN FORENSIC CASEWORK .1. MIXTURES, AGING, DEGRADATION AND SPECIES STUDIES

We have evaluated a multiplex STR system for routine forensic use, whi ch co-amplifies six short tandem repeat (STR) loci; HUMTH01, D21S11, D 18S51, D8S1179, HUMVWF31/A and HUMFIBRA (FGA), in conjunction with the X-Y homologous gene Amelogenin. Analysis of PCR products employs dena turing polyacrylamide gels coupled with fluorescentlabelled primers an d detection is undertaken on ABD 373A automated sequencers. The techni que was shown to be robust and reproducible when samples were analysed under conditions consistent with those encountered in a forensic envi ronment. The system was demonstrated to be human specific and is suita ble for use with both aged and degraded material. Somatic stability wa s proven with a wide range of tissue types and we were able to detect mixtures at ratios between 1:10 and 10:1. During this study no inciden ce of sample mis-typing due to allelic or locus drop-out was observed. Furthermore, although additional artefact bands were occasionally enc ountered these did not interfere with the interpretation of results. T he performance of the system with poor quality samples demonstrated it s suitability as a powerful tool in forensic investigation.