Evaluation of the potential of serum cortisol level and expression of StAR gene as biomarkers to establish the nature of sexual act

Forensic investigation of sexual assault cases possesses huge challenges viz., limited sample quantity, attributing the partner, and identifying the nature of the sexual act. Though forensic DNA evidence might correctly identify an accused, its biggest limitation is to overcome the consent defense which holds significant legal implications. Routinely, the examination of anogenital injury establishes the nature of a sexual act. However, it suffers major limitations as the prevalence of anogenital injury has also been observed commonly after a consensual sexual act. The present study compared the perceived stress, serum cortisol level, and the expression level of the StAR gene in 20 survivors of sexual assault and 20 consensual sexual partners. The average perceived stress scale was observed to be 32.1 ± 1.3 and 17.6 ± 0.5 in sexual assault survivors and consensual partners, respectively. The serum cortisol level showed a 1.183 to 3.176 fold increase in the survivors of sexual assault compared to the partners of the consensual sexual act. Compared to the consensual partners, sexual assault survivors showed a 19.508 to 144.664 fold increase in the expression of the StAR gene in blood. Besides, a significant positive correlation was observed among the PSS, cortisol level, and expression level of the StAR gene (R² = 0.878) (P < 0.001). Thus, in addition to the external injury examination, other biochemical and molecular examinations such as PSS, serum cortisol level, and expression of StAR gene have shown the potential to establish the nature of a sexual act.