Makkot 7: Murder and Degrees of Unintentional Killing

Last mishnah of the chapter: After the witnesses have testified, and the court has issued its verdict (a death sentence), and the defendant runs away... and he comes back, but is not judged again. Rather, witnesses testify to the previous judgement. Plus, the concern about a court being a "bloody court" for sentencing however many to death - and the concern that no death sentences (so the court would never be a bloody court, but, at the same time, murderers would be getting away, as it were). Also: Chapter 2! With a new mishnah - and unintentional killing which may allow the killer to take refuge in a city of refuge, protected from an avenging relative. But not every unintentional killing has that protection. Also, another mishnah! What happens if a person is chopping with an axe and the axe-head - or the wood - flies through the air and kills another... would that woodchopper be able to be exiled to the city of refuge?