What is the duty of the police to seize evidence from the scene of a crime?

A duty to seize evidence logically arises at the time a crime is first investigated. Recognizing a limited duty on the police at that point in the criminal process "ensure[s] that rights recognized at one stage ... will not be undercut at other less visible, stages" and "make[s] of the trial a search for truth informed by all relevant material." (United States v. Bryant, supra, 439 F.2d at pp. 642, 648.) Such a duty does not place undue burdens on the government but ensures that the trial is a bona fide search for truth.