A prisoner sentenced to death, can he/she commit suicide before the fulfillment of the sentence?

Random thoughts: I was just wondering, those prisoners sentenced to death by law, what if they want to commit suicide instead of going through a painful death like Electric Chair / Hang / Poison Injection & etc? Will the government save them from doing such attempt to commit suicide? Or will they be like; anyway he/she sentenced to death so let him/her die?