How long does semen stay in the body AFTER SEX?

Up to 7 days.

Research indicates that semen and male DNA can persist in the body for several days, and in some circumstances for up to around seven days. Levels decline rapidly over time, particularly within the first 24–48 hours after intercourse.

Read an acquittal case where semen was detected and time since intercourse was a question for the jury:How DNA Evidence Is Used in Sexual Assault Cases - A Real Case Explained

Laboratory testing may detect seminal fluid or male DNA hours or days later, depending on biological processes, washing, movement, and the way samples are collected. As time passes, the quantity of material typically decreases and detection becomes less likely.

Importantly, the detection of semen or male DNA cannot determine when intercourse occurred. It cannot distinguish between recent activity and earlier consensual contact, and it does not establish timing with precision. A suitably qualified expert may, however, undertake what is known as a time-since-intercourse evaluation to assess whether the scientific findings align with the alleged timeframe or an alternative account.

For this reason, semen findings must be interpreted alongside all other information in a case, including timelines, reported activity, prior contact, and the potential for transfer or persistence.

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