Fuzz: When Nature Breaks the Law

by Mary Roach

Much can be learned from blood at a crime scene. Round drops on the ground suggest a “gravity pattern”: blood falling by its own weight from a wound. Oblong gravity drops suggest a victim running as he dripped. A “force-related pattern”—blood ejected by the force of, say, a paw swipe or the pressure of a major artery—is elongated, with a tail like a comet. It’s a spatter, not a drip. Someone finds a trail of drips. Joel tells us to look closely at their size. When drips of blood grow smaller as the trail progresses, they’re probably not coming from a wound. They might be dripping from the animal’s fur, or a murderer’s blade. If the size of the drips remains constant—a “replenishing trail”—they are likely coming from an “active bleeder.” A smear of blood is a “contact pattern,” perhaps a place where the victim fell or placed a bloody hand.

Wasn’t blood spatter analysis discredited (for human crime anyway)?