Objectives: 

Identification of foreign biological material by genetic profiling is widely used in forensic DNA testing in different cases of sexual violence, sexual abuse or sexual harassment. In all these kinds of sexual assaults, the perpetrator could constrain the victim to kissing. The value of the victim's saliva taken after such an assault has not been investigated in the past with currently widely used molecular methods of extremely high sensitivity (e.g. qPCR) and specificity (e.g. multiplex Y-STR PCR).

Materials: 

Twelve voluntary pairs were tested at various intervals after intense kissing and saliva samples were taken from the women to assess the presence of male DNA. Sensitivity-focused assays based on the SRY (single-copy gene) and DYS (multi-copy gene) sequence were used to confirm the presence of male DNA. For specificity, standard multiplex Y-STR PCR profiling was performed.

Results: 

Male DNA in female saliva was proved after 10 and even 60 minutes after kissing, respectively. Using standard multiplex Y-STR PCR profiling male DNA was found in female saliva samples, as the entire Y-STR profile, even after 30 min in one sample.

Conclusions: 

Foreign DNA tends to persist for a restricted period of time in the victim's mouth, can be isolated from saliva after prompt collection and can be used as a valuable source of evidence.