The importance of staff genetic profiles in DNA databases

Abstract

The Portuguese Law no. 5/2008, published on the 12th of February of 2008, approved the creation of the DNA profile database for civil and criminal investigation. The first DNA profile was inserted in 2010 and in December of 2023 the DNA Database had a total of 23775 genetic profiles, 67% of which from convicted offenders, 30% from crime scene evidence for criminal investigation and 2% from staff. The 1% left are profiles for civil identification proposes as well as volunteers for civil and criminal investigations. The primary objective of forensic DNA databases is to help criminal investigations, by producing matches to enable the identification of profiles from crime scene evidences, and to help civil identification through matches between profiles of unidentified corpses and profiles obtained from missing person objects or relatives of missing persons. Until December 2023, Portuguese DNA database produced 989 matches at national level, 39% were between profiles obtained from evidence samples of criminal investigation, around 60% resulted between profiles from crime scene evidence with convicted offenders and around 1% were between profiles from collected evidence and staff. The Portuguese DNA database counts with 564 staff profiles, which leaded to nearly 1% of the national matches. From these eight matches obtained from crime scene investigation, three were with single profiles and the other five were with mixture profiles. One of the mixture profiles matched with two different staff profiles, resulting this combination in a perfect match. According to the ENFSI’s recommended guidelines, every person who could introduce cross -contamination to the investigated DNA samples, should have their profile inserted in a laboratory elimination DNA database and in the national DNA database. The aim of this work is to emphasize the importance of the inclusion of the staff profiles in the national DNA database, leading to identify genetic profiles that were assumed as evidence and therefore could help to solve an investigation. However, as a result of contamination, should not be considered.