Mercy should always triumph over judgement (Jam 5:13). For the death penalty to be implemented, a group of witnesses, judges and community leaders would each have to be willing to enforce it. If just one judge or witness were squeamish, the death penalty would be commuted. This would make the death penalty quite rare. The crime would have to be sufficiently horrendous to overcome their revulsion towards the death penalty. They could not pretend that it was not happening, but would have to look the murderer in the eye.
Most judges and witnesses would choose mercy, especially if the criminal was willing to pay a ransom. If there were any doubt about guilt or any extenuating circumstances, they would refuse to implement the death penalty to avoid being guilty of killing an innocent person. If a criminal has repented and made peace with God, they would prefer a ransom to a death penalty. God’s justice leaves room for mercy.
On the other hand, some murders are so horrendous, that a death penalty seems to be the only just penalty. A person who sadistically kills several people or tortures and kills children seems to deserve a harsh penalty. Some repeat offenders are so incorrigible, that society may need to be protected from them. Locking them up for a lifetime is cruel and costly, so the death penalty might be a kinder solution. I suspect that in these situations, a community would be willing to implement a life sentence. They would also be unwilling to accept a ransom.