Why We Let a Guilty Man Go Free

It' s interesting to read all these cases in Criminal Procedure where the Court ultimately suppresses evidence that, while seized in an unConstitutional fashion, nonetheless inculpates the defendant. I turn to "A Man for All Seasons" as the proper justification:

Setting - Sir Thomas More has declined to employ Richard Rich, who has just left the room.

Speaker	Dialog
Wife	Arrest him!
More	For what?
Wife	He's dangerous!
Roper	For all we know he's a spy!
Daughter	Father, that man's bad!
More	There's no law against that!
Roper	There is, God's law!
More	Then let God arrest him!
Wife	While you talk he's gone!
More	And go he should, if he were the Devil himself, until he broke the law!
Roper	So, now you give the Devil the benefit of law!
More	Yes! What would you do? Cut a great road through the law to get after the Devil?
Roper	Yes, I'd cut down every law in England to do that!
More	Oh? And when the last law was down, and the Devil turned 'round on you, where would you hide, Roper, the laws all being flat? This country is planted thick with laws, from coast to coast, Man's laws, not God's! And if you cut them down (and you're just the man to do it!), do you really think you could stand upright in the winds that would blow then? Yes, I'd give the Devil benefit of law, for my own safety's sake!

Available at http://www.radix.net/~bbrown/amfas.html. See also Chimel v. California, 395 U.S. 752, n. 12 (1969) ("The [Fourth] Amendment is designed to prevent, not simply redress unlawful police action.")