Deterrent means to prevent. To deter, keep from happening. Once the murder has been committed, it is impossible to prevent it from happening. Putting the murderer in prison for life will keep it from being repeated. As far as deterring future murderers, the death penalty doesn't do it. Stats show that murderers are not likely to take the death penalty into account before committing murder. Another factor is putting to death innocent people. It has been done before and is bound to happen again. As a decent society, we should not take the chance of putting innocent people to death.