A Comparison of Saliva and DNA Transfer and Persistence on Skin Immediately and 6 h Following Biting, Kissing, Licking and Sucking
Year: 2026
Type: article
Abstract: BACKGROUND: The presence or absence of saliva and saliva-derived DNA may be relevant to a range of different crime types, including sexual assault and homicide offences, where allegations of saliva transfer to the skin of a victim or offender from actions such as biting, kissing, licking or sucking are relevant. The interpretation of skin samples following allegations of biting, kissing, licking or sucking requires an awareness of the prevalence, transfer and persistence of saliva, and its DNA composition, including self- and non-self DNA, with and without such activities occurring. The matter of persistence is especially important given that the examinations of suspects or victims do not often occur immediately after the offence. METHODS: This study investigates the transfer of saliva onto human skin and its persistence following actions of biting, kissing, licking and sucking. Seven male-female couples were asked to shower and then bite, kiss, lick and suck separate defined areas of both of their partner's arms. Following these different actions, one arm was sampled immediately, and the other arm was sampled 6 h later. Background (prior to shower) and control (post-shower but before deposition) samples were also obtained. For participants who wore long-sleeve clothing post-activity, the inner sleeves were also sampled along with the tested skin areas at 6 h sample collection. Presumptive saliva tests were carried out on all background, control, 6 h experimental and clothing samples collected, using the RSID-Saliva immunological test kits. All recovered samples (immediate, persistence, clothing, background and control) underwent DNA extraction and quantification, and all background, 6 h and clothing samples were STR-amplified, generating DNA profiles. RESULTS: The results were considered with the questionnaire data provided by participants, to assess what factors may have influenced the presence or absence of any saliva, self (donor), partner or foreign DNA detected. Comparisons of the DNA quantities recovered from the immediate samples and 6 h samples were made. Furthermore, saliva detection rates of 6 h samples and DNA profile data were compared between all samples generated from the four different actions which resulted in saliva transfer to skin. Concussions: This research will assist forensic investigators when interpreting saliva DNA evidence recovered from the skin of victims or suspects after a prolonged period of time between the offence and collection.
Source: Genes
Institutions: Flinders University, Victoria Police, La Trobe University
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $3,137
OpenAlex ID: W7220391209