English Explanation of Mishnah Sanhedrin 8:7

The following can be saved [from sinning] even at the cost of their lives: he who pursues after his neighbor to slay him, [or] after a male [to rape him], [or] after a betrothed maiden [to rape her].
But he who pursues after an animal [to have relations with it], or one who would violate the Sabbath, or commit idolatry, must not be saved [from sinning] at the cost of his life.
The final mishnah of chapter eight continues to discuss this concept of “preventive punishment” and its limited applicability in Jewish law.
The principle of preventive punishment is a dangerous principle for even a court cannot tell with certainty if someone will surely commit a crime in the future. The Rabbis recognized the danger of this principle and therefore limited its applicability. Section one teaches that one may be killed preemptively only if he was about to commit a capital crime that would violate another person. Section two lists cases in which a person may be killed preemptively, even though he is about to commit a capital crime. Since none of these sins are crimes against other people, the only way the criminal can be executed for having committed one of them is by a proper trial done in front of a court of twenty three.