Then Jael, Heber's wife, took a nail of the tent, and took a hammer in her hand, and went softly unto him, and smote the nail into his temples, and fastened it into the ground: for he was fast asleep and weary. So he died.

And somme han drive nayles in hir brayn
Whyl that they slepte, and thus they han
hem slayn.

The nail murder is one of the most famous motifs in Chinese crime literature. The oldest source is quoted in the casebook T'ang-yin pi-shih, where the solution is ascribed to Yen Tsun, a clever judge.
The point of these stories is always the same: the judge is baffled by the fact that although there are strong reasons for suspecting the wife, the body of the husband shows no signs of violence. The final discovery of the nail is elaborated in various ways.
The oldest version said that Yen Tsun found it because he noted that a swarm of flies congregated on one place on top of the dead man's skull...
In 1881, Stent recorded another version under the title 'The Double Nail Murders' in volume 10 of the China Review: When the coroner fails to discover any trace of violence on the victim's corpse, his own wife suggests to him that he look for a nail. When the judge has convicted the murdered man's widow on this evidence, he also has the coroner's wife brought to him, since her knowledge of such a subtle way of committing a murder seems suspicious to him. It transpires that the coroner is her second husband. The corpse of her first husband is exhumed, and a nail discovered inside the skull. Both women are executed.