From the early annals of Law & Economics:
[T]here is nobody that knoweth not how unreasonable, yea, how pernicious a thing it is to the weal public, that a thief and an homicide or murderer, should suffer equal and like punishment. For the thief seeing that man, that is condemned for theft in no less jeopardy, nor judged to no less punishment, than him that is convict of manslaughter; through this cogitation only he is strongly and forcibly provoked, and in a manner constrained to kill him whom else he would have but robbed. For the murder once done, he is in less care, and in more hope that the deed shall not be betrayed or known, seeing the party is now dead and rid out of the way, which only might have uttered and disclosed it. But if he chance to be taken and descried, yet he is in no more danger and jeopardy, than if he had committed but single felony. Therefore whiles we go about with such cruelty to make thieves afraid, we provoke them to kill good men.--More, Utopia (Raphael Hythloday to John Morton, Archbishop and Cardinal of Canterbury, and at that time also Lord Chancellor of England).
Raphael Hythloday's argument presupposes that criminals respond to incentives and make a rational cost-benefit analysis. Harsh laws that are said to deter crimes can, in fact, create incentives to commit even more crimes (say, by encouraging the elimination of pesky witnesses at no further cost to the criminal). Of course, it is possible that the Sovereign's incentives may not reside in preventing crimes; Hythloday insinuates in the text that the Sovereign is primarily interested in obtaining fines from criminals and recovering for himself "the thief-stolen thing." Moreover, a fearful, mutually suspicious and "troublesome and noyous in peace" population has other advantages to a Sovereign. Such a population desires a strong Sovereign, and is easier held in awe of it.
No wonder that governments promote tough-on-crime laws.