DNA mixtures in forensic casework: a 4-year retrospective study

Variability in the detection of mixed profiles in four commercial autosomic STR multiplexes

“…Concordance in allele designation was higher in D5 and D19, both markers are in first position in their fluorochrome groups and they are present in only two kits. The analysis by the different position of the STRs in each fluorochrome group in each kit support our previous observations [3], with average detections of 35 mixed samples in first position, 32 in second, 26 in third, 17 in fourth and 13 in fifth (only D2 in Idf); the analysis by fluorochromes showed than STRs labelled in yellow yielded a slightly lower incidence in the detection of mixtures (51%) than the other colours (red and green 56% and blue 55% average of samples with at least three alleles over 100 RFUs). The presence/absence of some markers seems to be an important factor in the capacity of mixture detection for a kit.…”

“…DNA extracts of 55 non-probative mixed evidences, selected from samples included in a previous study [3] Cofilerk (Co), Identifilerk (Idf) and SGMPlusk (SGM+ in the text) kits (Applied Biosystems), according to the manufacturers' instructions. The DNA extracts had been stored at À 20 8C during a period of 5 to 10 years.…”

Validation of a combined autosomal/Y-chromosomal STR approach for analyzing typical biological stains in sexual-assault cases

“…Closer inspection revealed that stains from these cases typically consisted of visible bodily-fluids on victim's clothing (these fluids were supposed to be female because they tested negative for semen), including hidden touch DNA from a male contributor. Here, Y-STR analysis selectively identified a male component in a high female background to yield a single-source Y-STR profile, whereas autosomal analysis failed due to preferential amplification [17][18][19]. Comparable results were obtained for vaginal, anal, or oral swabs from the interior of the body of the victim.…”

Inference about the number of contributors to a DNA mixture: Comparative analyses of a Bayesian network approach and the maximum allele count method

“…The reason for this is that -from a practical point of view -it is of interest to detain information about the performance of inference approaches for the number of contributors in repeated trials where each trial may involve one of several distinct numbers of contributors, rather than a given constant number of contributors. Although in practical work it may not precisely be known at which proportion the various possible numbers of contributors appear, these proportions can nonetheless be framed in reasonable orders of magnitude (based, for example, on empirical studies (e.g., [13]). Here, the analyses reported several such proportions.…”