Recognizing the advantage of employing the PowerPlex(®) ESI and PowerPlex(®) ESX complementary kits for purposes of clarification in routine casework

Abstract

In an effort to promote European cross-border cooperation in fighting crime and international terrorism the Treaty of Prüm was drafted and accepted within the European forensic community. This move led to the commercial development of new multiplex kits which introduced five new STR loci and promised better performance. Recently the Israel Police DNA Casework and Database laboratories adopted the PowerPlex(®) ESI kit for routine use in our laboratories. Presented in this paper are examples of three types of ambiguous results encountered during the implementation of the PowerPlex(®) ESI kit into routine work. These ambiguous products presented themselves in the form of (1) extreme variants outside of loci borders, (2) failure to amplify sister allele pairs or expression of null alleles and (3) episodes of loss of separation of adjacent microvariants primarily in mixture samples. The re-analysis of all these samples using the PowerPlex(®) ESX kit successfully and rapidly clarified all three categories of anomalies. Spotlighting such events to the forensic community, especially regarding the novel loci introduced in these next generation kits, can aid in raising the analyst's awareness to their future appearances and prevent possible erroneous conclusions. In addition, providing timely DNA results to investigating teams is of great importance and operational forensic laboratories do not have at their immediate disposal methods such as sequencing to elucidate such manifestations. We suggest that the complementary use of the PowerPlex(®) ESI and PowerPlex(®) ESX can provide a benefit for clarification purposes in routine casework.