CIUDAD JUÁREZ, Mexico — Alejandro Hernández Cárdenas took a scorched-looking, decomposed head and five stiff, bloated hands and gently submerged them in his secret solution. After they soak for three days, he said, any scars, lesions or birthmarks the victim might have had will reappear.

They did. The putrid head looked human again, with full lips, large pores and a massive bruise on the forehead. The hands had recovered their identifying prints.

“Science advances,” said Dr. Hernández Cárdenas, “whenever there are difficult situations.”

The newly revealed details may never lead to a conviction, or even an arrest, but Dr. Hernández Cárdenas, a forensic odontologist who works in the Ciudad Juárez Forensic Science Lab, has attained the kind of star status that could be produced only in a city like this, with its semidesert climate, exorbitant murder rate and can-do frontier creativity. Dr. Hernández Cárdenas developed the rehydration technique, which he primarily uses on full bodies, more or less single-handedly, and he even pays part of the cost for the chemicals that turn back the clock on his brittle subjects.

Forensic experts have long used glycerin injections to reconstitute fingers to get prints, but that is not practical for entire bodies — particularly not in the scorching heat of Ciudad Juárez, where bodies decompose and mummify quickly. Only through rehydration does the corpse regain some of its original condition, helping the police by revealing lesions and bringing internal organs back to nearly their state at the time of death.