Final answer:
The defender of the Best Bet Argument believes that retaining the death penalty risks killing an innocent person due to the possibility of wrongful convictions. This argument considers the moral implications of executing an innocent individual.
Step-by-step explanation:
The defender of the Best Bet Argument argues that by retaining the death penalty, we risk doing the bad thing of killing an innocent person. The argument suggests that there are cases where an innocent person may be wrongly convicted and put to death. While the death penalty may deter some crime, the risk of executing an innocent person is seen as morally unacceptable by the defender of this argument.