The wrist theory originated with Pierre Barbet, a French battlefield surgeon who studied the Shroud of Turin in the 1930s. In a cadaver experiment, Barbet drove a nail into the soft center of the palm and found it tore free under weight. Rather than testing other points in the palm, he concluded no part of the palm could bear the body's weight, and proposed the nail instead passed through Destot's space, a gap between the wrist bones. He argued this location matched the wound on the Shroud and, he claimed, would sever the median nerve — which he offered as an explanation for why the Shroud shows no visible thumbs.
Decades later, forensic pathologist Frederick Zugibe — a medical examiner with a Ph.D. in anatomy, and so arguably better equipped than Barbet to match wound evidence — ran more extensive cadaver experiments. He found a passage through the palm itself, between the bones supporting the index and middle fingers, that could bear the body's weight without tearing or breaking bone. A nail there angles back through the hand and exits at a point Zugibe argued matches the Shroud's wound more precisely than Barbet's wrist site — and lines up with wounds reported in stigmatists like Padre Pio. Zugibe also showed Barbet's wrist location would actually miss the median nerve, and proposed instead that the thumbs simply disappear from view because the wrist relaxes and drops after death.
Casey ties this to the older historical record: New and Old Testament texts refer to "hands," not wrists; the earliest surviving Crucifixion depictions (a British Museum ivory from around AD 420 and a Roman door panel from AD 430–432) show nails in the palms; and the wrist theory itself dates back only to Barbet's work in the 1930s, versus roughly 1,900 years of prior consensus. Casey's conclusion is that the Shroud, often cited in favor of the wrist theory, may actually support the traditional palm placement instead.