What happens to blood after a person dies?
After death, blood normally coagulates unless the deceased has ingested certain medications or chemicals (e.g. anti-coagulants).

According to this article, normal clotting time is 3-15 minutes: http://www.angelfire.com/sc3/cjrp/forensicsofdeath.html

However, this probably applies to external wounds, like cuts. When a person dies, the blood pooled internally would probably take longer to coagulate. You might find the answer by typing blood + coagulate + forensics into Google.