Telltale Blood

ba-BUM…ba-BUM…ba-BUM…listen! Is that a “tell-tale heart?”

This is Sandra Tsing Loh with the Loh Down on Science.

You’ve seen the crime TV shows. A forensic expert recreates the scene of the crime just by looking at the blood spatters. From this, they solve the case! Well, not so fast, says physics.

Alexander Yarin, from the University of Illinois, Chicago, and colleagues study blood spray from gunshot wounds. They shoot firearms at blood-soaked sponges from different distances. The blood gets sprayed across the room. Then comes the messy bit—analyzing the spray for patterns.

Results? Muzzle gas from the gun can blow blood spray around in weird ways! That means blood spatter isn’t as reliable as the TV would tell you. And, it means current forensics may need to be careful how they interpret a scene.

This could be good or bad depending on who you are. For some, it could mean that they were wrongly accused. But for others, it may mean they got away with murder!

Understanding physics can help blood tell the truth.