Deuteronomy 21:3
And it shall be, that the city which is next unto the slain man, even the elders of that city shall take an heifer, which hath not been wrought with, and which hath not drawn in the yoke; And it shall be, that the city which is next unto the slain man, even the elders of that city shall take an heifer, which hath not been wrought with, and which hath not drawn in the yoke;
When a killing is left without a known murderer, the law lays the burden on the leadership of the city found closest to the dead person. Those elders are to take a young female cow that has never been put to labor and has never pulled under a yoke, and to use it in a solemn ceremony carried out before the people. The rite declares that the taking of life is never to be passed over lightly, but obliges those in authority to search hard for the one who did it and to make public their hatred of the deed. Any careless neglect that protects the wrongdoer brings the guilt of shed innocent blood upon the community itself.