Assuming this was a multiple-choice question and you had to choose between the following:
The answer is: "The authors speculate that this finding may not seem so bizarre if one considers executions as acts of aggression that might lead to imitation (1)."
An overwhelming majority of criminologists and social psychologists believe that death penalty does not act as a deterrent to prevent homicides, and it is widely accepted in social science that the number of murders (either increasing or decreasing) is very slightly affected by the enforcement of death penalty.
However, it has also been observed that the exposure to public executions or the publicity around the death penalty tended to provide people with models of violence, which raised the probability of criminal activity.