Impact on touch DNA of an alcohol-based hand sanitizer used in COVID-19 prevention.

In the last years, forensic research has been focused on touch DNA in order to improve its evidential value in criminal activity investigations as well as to understand the variables impacting touch DNA. One of the emerging variables is represented by the use of alcohol-based sanitizers, which was suggested for hand hygiene during the COVID-19 pandemic. The aims of the present study were to assess the effect of a hand sanitizer on touch DNA deposition, transfer, and recovery and also to evaluate STR typing success, quality of DNA profiles, and personal identification. Before and after the use of an alcohol-based hand sanitizer, 20 volunteers deposited on glass surfaces 120 fingerprints, containing skin-derived or salivary DNA. Samples were quantified by real-time quantitative PCR (q-PCR), and 76 samples yielding > 15 pg/µl were typed for 21 autosomal STRs by GlobalFiler® PCR Amplification Kit. DNA profiles were classified into single source, mixed, and inconclusive profiles, and a LR assessment was performed by comparison to the reference samples using LRmix Studio software. After the use of hand sanitizer, samples yielded lower quantities of recovered transferred DNA, especially considering samples containing salivary DNA (p < 0.05 by Friedman test). All the 76 amplified samples (63.3% of the total) showed at least 10 typed loci, and 83-100% of profiles were consistent with the reference ones on the basis of a LR value ≥ 106. Results showed that, although the hand sanitizer reduces the DNA recovering, touch DNA samples might still be useful for forensic personal identification even when hand sanitizers are used.

Human DNA contamination of postmortem examination facilities: Impact of COVID-19 cleaning procedure.

The DNA contamination of evidentiary trace samples, included those collected in the autopsy room, has significant detrimental consequences for forensic genetics investigation. After the COVID-19 pandemic, methods to prevent environmental contamination in the autopsy room have been developed and intensified. This study aimed to evaluate the level of human DNA contamination of a postmortem examination facility before and after the introduction of COVID-19-related disinfection and cleaning procedures. Ninety-one swabs were collected from the surfaces and the dissecting instruments, analyzed by real-time quantitative PCR (q-PCR) and typed for 21 autosomal STRs. Sixty-seven out of 91 samples resulted in quantifiable human DNA, ranging from 1 pg/µl to 12.4 ng/µl, including all the samples collected before the implementation of COVID-19 cleaning procedures (n = 38) and 29 out of 53 (54.7%) samples taken afterward. All samples containing human DNA were amplified, resulting in mixed (83.6%), single (13.4%), and incomplete (3%) profiles. A statistically significant decrease in DNA contamination was found for dissecting instruments after treatment with chlorhexidine and autoclave (p < 0.05). Environmental decontamination strategies adopted during COVID-19 pandemic only partially solved the long-standing issue of DNA contamination of postmortem examination facilities. The pandemic represents an opportunity to further stress the need for standardized evidence-based protocols targeted to overcome the problem of DNA contamination in the autopsy room.