The death penalty dramatically signifies that society does not excuse or condone the taking of innocent lives. It symbolizes the value of the innocent victim. Incapacity can be imposed by long terms ofimprisonment, particularly for habitual offenders; the policy of "keeping criminals off the streets" does indeed protect the public for a period of time, although it is done at a considerable cost. The object of deterrence is to make the certainty and severity of punishment so great as to inhibit potential criminals from committingcrimes. The best available estimates of the certainty of punishment for serious crime suggest that very few crimes actually result in jail sentences for the perpetrators.