Is it permissible for someone unjustly sentenced to death to kill himself to avoid the expected brutal and painful method of execution?

The fear of being killed does not in any way permit a Muslim to kill himself, for it is one of the gravest sins. Allah, the Exalted, says: "And do not kill yourselves. Indeed, Allah is to you ever Merciful." The oppressed person must defend himself, and if he is killed, then he is a martyr and not a suicide; for the Messenger of Allah, may Allah bless him and grant him peace, said: "Whoever is killed defending his wealth is a martyr; and whoever is killed defending his religion is a martyr; and whoever is killed defending his blood is a martyr; and whoever is killed defending his family is a martyr."