Y-chromosome STR marker database increases the resolution of sexual crimes in the state of Goiás, Brazil

Abstract

As the vast majority of sex crimes are perpetrated by men, Y-STR molecular markers have become a valuable tool in criminal investigations. The Y-chromosome has shown promise in the identification of male DNA from samples, especially when this DNA occurs in small amounts or is mixed with genetic material of female origin. Given the high risk of recidivism among sexually violent offenders, the present study evaluates the effectiveness of an in-house Y-chromosome STR marker genetic profile database (BPG-YSTR) as a tool in the investigation of sex crimes in the state of Goiás, Brazil. We analyzed cases of sexual violence involving biological samples that tested positive and negative for spermatozoa. DNA extraction was performed by differential lysis using the PrepFiler Express™ (Applied Biosystems®) kit. DNA quantification was performed by Real-Time PCR, while amplification was performed with commercial multiplex AmpFlSTR ®Yfiler™ (AppliedBiosystems®), PowerPlex® Y23 (Promega) or Yfiler™ Plus (AppliedBiosystems®) kits. Amplification products were separated by capillary electrophoresis in the ABI 3500 genetic analyzer®(AppliedBiosystems®). The inclusion of 595 haplotypic profiles in the BPG-YSTR identified genetic matches between biological evidence samples of sexual crimes involving 28 offenders and 127 victims. In 19.8% of the cases, the matches were identified exclusively by the BPG-YSTR, which means that analyses involving Y-chromosome markers added valuable information to the investigation of serial crimes in almost 1/5 of the cases. Therefore, Y-STR specific markers were shown to be a promising tool for criminal investigations involving sexual crimes.