Foreign DNA in cosmetic gel nails

In this case study it was investigated whether foreign DNA may get encapsulated in a cosmetic gel nail. It was inspired by a murder case in which the main suspect claims that he was wrongly convicted. Most of the evidence in the case was circumstantial. The most direct piece of evidence was DNA of the suspect found beneath the victim's fingernails. According to the prosecution and the judges, the DNA meant that the suspect had murdered the victim. However, according to the suspect, the fact that his DNA was found could be explained by a physical altercation between him and the victim 17 days prior to the murder. In that alternative scenario, the suspect's DNA became encapsulated in the victim's gel nails and remained there up until her death 17 days later. In this article, we describe an experiment designed to assess the plausibility of the alternative scenario. In the experiment we tested whether foreign DNA could be recovered in gel nails of four female individuals two weeks after transfer. In six out of eight hands the profile of the donor could be detected. Hence, in situations resembling the circumstances of this case study, the encapsulation of DNA in a gel nail prior to the attack of interest must be considered.