While the machinery of law enforcement and indeed the nature of crime itself have changed dramatically since the Fourth Amendment became part of the Nation's fundamental law in 1791, what the Framers understood then remains true today - that the task of combating crime and convicting the guilty will in every era seem of such critical and pressing concern that we may be lured by the temptations of expediency into forsaking our commitment to protecting individual liberty and privacy.

No doubt, there are those who believe that judges - and particularly dissenting judges - write to hear themselves say, as it were, 'I, I, I.' And no doubt, there are also those who believe that judges are, like Joan Didion, primarily engaged in the writing of fiction. I cannot agree with either of those propositions.

At bottom, the battle has been waged on moral grounds. The country has debated whether a society for which the dignity of the individual is the supreme value can, without a fundamental inconsistency, follow the practice of deliberately putting one of its members to death.

If there is a bedrock principle underlying the First Amendment, it is that the government may not prohibit the expression of an idea simply because society finds the idea itself offensive or disagreeable.

The concept of military necessity is seductively broad, and has a dangerous plasticity. Because they invariably have the visage of overriding importance, there is always a temptation to invoke security "necessities" to justify an encroachment upon civil liberties. For that reason, the military-security argument must be approached with a healthy skepticism.

More fundamentally, however, the answer to petitioners' objection is that there can be no impairment of executive power, whether on the state or federal level, where actions pursuant to that power are impermissible under the Constitution. Where there is no power, there can be no impairment of power.

Perhaps the bleakest fact of all is that the death penalty is imposed not only in a freakish and discriminatory manner, but also in some cases upon defendants who are actually innocent.