What is the ruling regarding the oath when the killing occurs in a locality, and how is the *diyah* decided?

Primary text

Fifty men from the inhabitants of the locality where the deceased was found must swear by Allah that they did not kill him nor do they know the killer, and they must pay the blood-money (*diyah*). This is based on the ruling of 'Umar, which, as far as is known, had no dissenting Companion, thus constituting a consensus (*ijma'*). This view is held by Al-Sha'bi, Al-Nakha'i, Al-Thawri, and the companions of 'A'i (i.e., the Hanafi jurists).