“How long can blood samples remain on crime sites?”

Because DNA and other components in the blood decay rapidly, a delay of longer than 48 hours may make the blood samples useless. It is an average of 72 hours after the crime to remove everythinhg. They call it the 72-hour rule. This is since they use the cut-off time to recover biological and trace evidence when it is more likely to be successfully collected. A range from 24 to 96 hours is more realistic. Thank you.

Blood stains can remain for very long periods of time, provided they are not wash away.

Dr. Felo

I think it depends on the type of surface, weather exposure, etc. You should refer your question to someone who works in forensic science.

RB Thomas, MD