Numbers 35:16-21, 24

“If anyone strikes a person with an iron object and death results, he is a murderer; the murderer must be put to death.  If anyone has in his hand a stone capable of causing death and strikes another person and he dies, the murderer must be put to death. If anyone has in his hand a wooden object capable of causing death and strikes another person and he dies, the murderer must be put to death. The avenger of blood himself is to kill the murderer; when he finds him, he is to kill him.  Likewise, if anyone in hatred pushes a person or throws an object at him with malicious intent and he dies, or if in hostility he strikes him with his hand and he dies, the one who struck him must be put to death; he is a murderer. The avenger of blood is to kill the murderer when he finds him.

the assembly is to judge between the person who kills someone and the avenger of blood according to these ordinances.