The DNA sample obtained from van den Hurk's remains was the prosecution's main piece of evidence in the 2015 trial. It was also used by the defence as evidence against the
manslaughter charges due to uncertainty surrounding the number of DNA profiles present in the samples.
Collection of DNA samples In 1995, van den Hurk's body was outside for nearly 7 weeks before being found. Three DNA samples were collected from her remains: two on the genital area and one on her underwear. These DNA samples were considered to be at high risk of contamination due to decomposition caused by exposure to bacteria and natural elements, and primitive DNA collection techniques of the time.
Analysis by experts Several DNA analysis experts from different forensic institutes were asked to research the complex mixed DNA samples for the 2014 trial, namely: • R. Eikelenboom (Independent Forensic Services), • J. Klaver-Koopman and T.J.P. de Blaeij (
Netherlands Forensic Institute), • J.S. Buckleton (
Institute of Environmental Science and Research in New Zealand), and • M.W. Perlin (chief scientific officer of U.S. company Cybergenetics) These experts presented their conclusions during the trial and were examined about their findings. The experts utilised various computer programs which analyse DNA profiles using statistical methods in a process called
probabilistic genotyping. These programs included: •
TrueAllele, developed by Cybergenetics, • LRmix Studio and MixCal, developed by the Netherlands Forensic Institute, and • STRmix, developed by J.S. Buckleton and colleagues at the Institute of Environmental Science and Research.
Test results The three DNA samples were analysed by the experts, but the results were inconclusive as the samples contained a complex mix of DNA profiles. The samples contained clear DNA profiles from two distinct males—believed by experts to be matches to de G. and van den Hurk's then-boyfriend—and some peaks that did not conclusively match either. The
issues with the DNA analysis led to speculation about another suspect that could exonerate de G. The DNA experts deliberated for years before coming to a conclusion, during which time wild speculations were made by the media, the defence team and the prosecution. The explanation from the experts about the inconclusive test results was misinterpreted by many as evidence for a "third DNA profile"; Nicole's stepfather and stepbrother were accused of being involved.
Trial conclusion and appeal The DNA analysis concluded that the DNA samples contained two distinct DNA profiles and a set of peaks which were inconclusive. The court came to the conclusion that, beyond a reasonable doubt, the two distinctive profiles were from Jos de G. and van den Hurk's then-boyfriend. Two possible explanations for the presence of the peaks were presented: • Contamination and DNA degradation, or • One or more contributors to the samples other than de G., van den Hurk, or her boyfriend. The uncertainty about the peaks would take years to be resolved, and would eventually be the basis for the prosecution's appeal. During the appeal, the
Dutch Supreme Court concluded that the second explanation was highly unlikely based on the evidence from the tactical investigations and forensic research of the case. Therefore, the possibility of other contributors to the DNA samples was eventually rejected by the Supreme Court on 21 April 2020. == Trial ==