The Torah obligates (Bamidbar 35:10-34) to designate six cities of refuge where someone who accidentally kills someone can immediately take refuge. The Book of Joshua (20:7-8) lists the six designated cities: Kedesh, Shechem, Hebron, Betzer, Ramot, and Golan.
By law, a relative of the deceased who attacks and kills the perpetrator of an accident is not held accountable. This rule does not apply in designated cities of refuge. Therefore, someone who accidentally kills someone must reach the nearest city of refuge as quickly as possible, as only there will they be legally protected.
If the court determines that the murder was premeditated, the perpetrator is sentenced to death (in the presence of witnesses and if a warning was given). If the court determines that the murder was an unforeseen accident, the perpetrator is released. If the court determines that the accident occurred as a result of gross negligence or carelessness, the culprit is sentenced to exile to a city of refuge, where he must reside until the death of the High Priest during whose reign the accident occurred. After the High Priest's death, he returns home.