Problems of Forensic Sciences 2001 Vol. 46 (XLVI) 116-124
APPLICATION OF GenePrint® PowerPlex™ 16 SYSTEM IN ANALYSING OF FORENSIC MIX STAINS
Paulina WOLAŃSKA-NOWAK, Wojciech BRANICKI, Tomasz KUPIEC
Institute of Forensic Research, Cracow, Poland
Streszczenie
The use of STR Multiplexes has become a routine procedure in profiling forensic stains. The GenePrint® PowerPlex™ 16 System allows the simultaneous coamplification and three-color detection of sixteen loci. It contains two new low-stutter, highly polymorphic pentanucleotide repeat loci, Penta E and Penta D, what makes it ideal for evaluation of DNA mixtures often encountered in forensic casework. The statistical treatment of mixed stains has been formulated in general mathematical approach by Weir et [7]. The strength of such evidence is represented by the Likelihood Ratio. The analysis requires the assignment of probabilities of all of the combinations of genotypes. Taking into consideration the area of peaks enhances the interpretation of DNA mix stains but involves the need to consider possible artefacts such as stutters [6]. DNA analyses were performed in the range of alleles included in PowerPlex™ 16 System. In the case when major/minor components cannot be distinguished, we used “dnamix” program of Weir. When the major/minor components can be established, the mixture proportions were estimated for all loci. The inference about suspect/victim match to the profile was described with Likelihood Ratio. We describe here three forensic cases where the above-mentioned analyses were successfully performed. At the first case the suspect set of alleles was find in the mix stain DNA profile taken from rubbery mask and the probability of this hypothesis was estimated. At the second case, the victims set of alleles was found in the mixed DNAprofile from the suspect’s night suit. It was estimated that the explanation that it was the victim’s material in the mixed profile was 50 000 more probable than under the hypothesis that it was of random origin. In the third case each of three assailants cell material were revealed in the mixed DNA profiles taken from three different fragments of stockings found at the crime scene. The presented examples of cases from our routine work examinations indicate usefulness of likelihood ratio approach, as theoretically justified by Evett and Gill [4], to estimation the value of DNA evidence, in the case of mixed stain.
Słowa kluczowe
Forensic mix stain; Multiplex; Interpretation.