Punish all individuals who violate the same norm in the same way. No exceptions, no mercy. Tipping is another consideration. It appears that certainty is not purely lineal in effect. That is, rather than increasing the deterrent effect with each incremental increase in the certainty of apprehension, a certain , consistent level of certainty must be reached in order to produce any desired consequences.
Overload is another problem.
As crime rates increase, police resources are stretched and the certainty of apprehension decreases. As crime rates decrease, police activity intensifies and certainty of apprehension increases. The causal mechanism is what is questioned here. Research on capital punishment indicates that the desired general deterrent effect may not be present. Also, there appears to be little, if any, difference in rates of capital offenses between states which impose the death penalty and those that do not.