Studies show that the cost of legal fees for the very long appeals process that someone on death row goes through is usually more than the cost of keeping that person in prison for life. Money shouldn't be the deciding factor for whether the death penalty is allowed or not, but capital punishment costs more money than life in prison in most cases.
- - - Post Merge - - -
Usually capital punishment is reserved for crimes that warrant life in prison, except in authoritarian governments who kill people for political purposes. So anyone who is facing the possibility of the death penalty is not getting a second chance either way.
Also, the death penalty usually makes the legal process more difficult for the victims' families. The death penalty phase and subsequent appeals process drags the ordeal out for the families and makes it more difficult for them to heal when they have to spend months or years involved in the legal process and they don't get a firm resolution to the case for a long time. For life in prison cases, things get wrapped up more quickly unless there is a mistrial or new evidence surfaces.