QI’m working on my third John Jordan novel and have a couple of questions. How long does it take blood to dry when someone is stabbed to death and loses a lot of blood? What are the factors that affect drying time? In my scenario, an inmate is murdered in his Florida jail cell in October. The blood is on the cement cell floor and the victim’s clothes.
Michael Lister
Florida Book Award—winning author of Double Exposure, The Body and the Blood, and The Big Goodbye
Panama City, Florida
ABlood clots in approximately five to fifteen minutes after exiting the body and will initially be dark maroon, gelatin-like, and sticky to the touch. Over a couple of hours it will gradually separate into a dark maroon-blackish clot surrounded by a pale yellow serum. This is due to contraction of the clotted blood and a “squeezing out” of the serum, which is not involved in the clotting process.
We do this in the lab quite often since many blood tests are done on the serum, while others are done on whole blood. The blood is allowed to clot in a test tube, and the tube is placed into a centrifuge and rapidly spun for several minutes. This pushes the clotted blood into the bottom of the tube, and the serum will float on top. The serum is then removed and used for various tests.
The blood on the floor will dry to a crusty brownish state over a few hours to three or four days, depending upon the actual temperature, humidity level, and the degree of ventilation. Warmer, drier, and breezy conditions would dry it faster. Blood on clothing is likely to dry faster than that on the floor since the clothing serves as a wick and spreads the blood over a larger area. If the clothing is placed inside a container or is wadded, it will take much longer to dry than if the clothing is spread out on the floor or draped over a chair or other object.
In your scenario, I’d allow at least six hours for the drying process to occur if the clothes are spread over something and twenty-four or more hours if not. Since you said that there is a lot of blood, it would take twenty-four hours or longer to completely dry on the floor unless someone spread it out in a thin layer. If so, it could also dry in six or so hours.