DNA transfer through nonintimate social contact.

Area of Science:

• Forensic Science
• Genetics
• Sexual Offense Investigation

Background:

• Interpreting sexual offense cases can be challenging when semen is absent but female DNA is present.
• Distinguishing between DNA transfer from sexual intercourse versus non-intimate contact is crucial for forensic investigations.

Purpose of the Study:

• To determine the frequency and amount of female DNA transferred to males' penises and underwear during non-intimate social contact.
• To compare DNA transfer from non-intimate contact with DNA transfer following unprotected sexual intercourse.

Main Methods:

• Simulated non-intimate social contact scenarios between males and females.
• Collection of penile swabs and underwear samples from males after contact.
• Analysis of DNA transfer using forensic genetic techniques.
• Comparison with DNA profiles obtained after unprotected sexual intercourse.

Main Results:

• No matching female DNA was detected on the inside front of underwear after non-intimate contact and secondary transfer.
• Significant female DNA profiles were found on the inside front of underwear after sexual intercourse (peak heights 1898-3157 rfu).
• Limited female DNA transfer to the waistband/outside of underwear was observed after non-intimate contact.

Conclusions:

• Female DNA on the inside front of male underwear is a strong indicator of sexual intercourse.
• Low-level DNA on the waistband (below 1000 rfu) may result from non-intimate contact and secondary transfer from hands.