On the issue of death penalty, a professor believes that killing pays for life. It is natural that severe punishment can prevent and prevent major crimes to a certain extent. For example, in the United States, the crime rate in the states with the death penalty is lower than that in the states without the death penalty. 
The law of the United States provides for prosecution in the place of crime and adjudication according to its law. Many criminals often commit crimes here.
 the death penalty can reduce crime.