Police still don’t know the origins of the human finger found in a bowl of Wendy’s chili in California last month. At one time, Nevada leopard-attack victim Sandy Allman was thought to be the finger’s likely original owner. But now investigators have concluded that the recovered finger isn’t hers. How can you identify a severed finger?
With fingerprints, DNA, and gross anatomy. Fingerprints are surprisingly resilient; a burnt or cooked finger with a damaged epidermis might still have a usable print on a deeper layer of skin. (A partial fingerprint taken from the Wendy’s finger failed to produce any leads.) DNA samples taken from a finger can also be used to certify a match to a specific person. If neither of these options works, the appearance and internal structure of the finger can provide some general clues.
The presence of nail polish or neat cuticles, for example, suggests that the finger comes from a woman. Dirt under the nail suggests otherwise. Forensic anthropologists can also draw some conclusions from the detached finger’s bone structure. The bones in a child’s fingers will have the growth plates characteristic of skeletal development. Older fingers are more likely to show symptoms of osteoarthritis at the joints.
The finger’s bone structure includes three phalanges and a metacarpal. The phalanges connect at the two finger joints and the knuckle; the metacarpal extends into the palm. (The thumb has only two phalanges and one joint.) By measuring the proportional dimensions of the metacarpal, investigators can sometimes determine the gender of the owner. The metacarpal can also be used to determine the identity of the severed finger—whether it’s an index (indicis), a middle (medius), a ring (annularis), or a pinky (minimus). But the bit of finger that was found in the bowl of chili, which is only 1.5 inches long, doesn’t appear to include any part of the metacarpal.
The digit’s outermost bone, the distal phalanx, can also yield some clues. The tip of the thumb looks quite different from the tips of the fingers: It’s wider and flatter, and there is a round pit on the inside of the bone facing the finger pad. The muscle that attaches to the thumb in this pit, the flexor pollicis longus, is what allows us to grab and hold objects between our thumb and fingers.
The other fingers can only be distinguished at the level of the proximal phalanx, the bone that goes from your knuckle to the second joint. In an index finger, this bone has a bulge at its base on the side nearest to the thumb. The proximal phalanx of the pinky has a smaller bulge on the side facing away from the ring finger.
The finger owner’s hobbies are sometimes revealed in the shape and structure of the bones. Radiographs of the fingertips of rock climbers, for example, show unusual bony spurs and thickened phalanges.
Explainer thanks Randall Susman of Stony Brook University, Anthony Falsetti of the C.A. Pound Human Identification Laboratory at the University of Florida, and Jon Nordby of Final Analysis Forensics.