Tractate Sanhedrin, Herbert Danby tr. , at sacred-texts.com
M.VIII. 7. These may be saved (from sin) at the cost of their lives: 1 he who pursues after his fellow to kill him, or after a male, or after a betrothed damsel. But he who pursues after a beast, or he who defiles the Sabbath, or he who commits idolatry, may not be saved (from sin) at the cost of his life.
11. He who pursues after a male, whether it be in a house or the open field, may be saved (from sin) at the cost of his life; if it be after a betrothed damsel, whether in a house or the open field, he may be so killed. If it be a betrothed damsel or any of the prohibited degrees enjoined in the Law, he may be so killed; but if it be a divorced widow of a high-priest, or an ordinary priest's wife who had been subjected to the ḥaliṣa ceremony, he may not be saved (from sin) at the cost of his life. R. Jehuda says: Also, should she say, "Let him alone!" he may not be so killed, even though by leaving him alone he commit a capital crime.
R. Eleazar, the son of R. Zadok, says: He who commits idolatry may be saved (from sin) at the cost of his life.
113:1 Cases of justifiable homicide.