What is the legal ruling and the punishment for a wife who kills her husband when he is caught in the act of adultery in her bed, and what are the legal proofs for that?

The crime of zina (unlawful sexual intercourse) is one of the gravest major sins. Its punishment becomes more severe if the fornicator is married, in which case the punishment is stoning to death.

It is not permissible for the wife to kill her fornicating husband. Rather, she must report him to the ruler (or authority) so that the prescribed punishment may be carried out against him.

If she kills him, she will be killed in retribution, unless he has a child with her, whether male or female, in which case the retribution is waived.