The purpose of punishment is to:
(a) the punishment of offenders,
(b) the reduction of crime (including its reduction by deterrence),
(c) the reform and rehabilitation of offenders,
(d) the protection of the public, and
(e) the making of reparation by offenders to persons affected by their offences.
A dead person cannot have reparations which go to their family.
The following is speaking about theft but we may apply this for minor crimes and where there is accidental, unintentional loss of life, and I have serious reservations applying this to deliberate murder.
5:39 Whoever repents after the crime and makes amends, God grants him pardon. God is Forgiving, Merciful. [If the hand is cut off, what about making amends, pardon and mercy?]