JUSTICE MARSHALL delivered the opinion of the Court.
The Due Process Clause of the Fourteenth Amendment requires the State to disclose to criminal defendants favorable evidence that is material either to guilt or to punishment. United States v. Agurs, 427 U.S. 97 (1976); Brady v.
The Omicron Intoxilyzer (Intoxilyzer) is a device used in California to measure the concentration of alcohol in the blood of motorists suspected of driving while under the influence of intoxicating liquor.
In unrelated incidents in 1980 and 1981, each of the respondents in this case was stopped on suspicion of drunken driving on California highways. Each respondent submitted to an Intoxilyzer test.
Prior to trial in Municipal Court, each respondent filed a motion to suppress the Intoxilyzer test results on the ground that the arresting officers had failed to preserve samples of respondents' breath. Although preservation of breath samples is technically feasible,
The California Court of Appeal ruled in favor of respondents. After implicitly accepting that breath samples would be useful to respondents' defenses, the court reviewed the available technologies and determined that the arresting officers had the capacity to preserve breath samples for respondents. 142 Cal. App. 3d, at 141-142, 190 Cal. Rptr., at 320-321. Relying heavily on the California Supreme Court's decision in People v. Hitch, 12 Cal.3d 641, 527 P.2d 361 (1974), the Court of Appeal concluded: "Due process demands simply that where evidence is collected by the state, as it is with the intoxilyzer, or any other breath testing device, law enforcement agencies must establish and follow rigorous and
Under the Due Process Clause of the Fourteenth Amendment, criminal prosecutions must comport with prevailing notions of fundamental fairness. We have long interpreted this standard of fairness to require that criminal defendants be afforded a meaningful opportunity to present a complete defense. To safeguard that right, the Court has developed "what might loosely be called the area of constitutionally guaranteed access to evidence." United States v. Valenzuela-Bernal, 458 U.S. 858, 867 (1982). Taken together, this group of constitutional privileges delivers exculpatory evidence into the hands of the accused, thereby protecting the innocent from erroneous conviction and ensuring the integrity of our criminal justice system.
The most rudimentary of the access-to-evidence cases impose upon the prosecution a constitutional obligation to report to the defendant and to the trial court whenever government witnesses lie under oath. Napue v. Illinois, 360 U.S. 264, 269-272 (1959); see also Mooney v. Holohan, 294 U.S. 103 (1935). But criminal defendants are entitled to much more than protection against perjury. A defendant has a constitutionally protected privilege to request and obtain from the prosecution evidence that is either material to the guilt of the defendant or relevant to the punishment to be imposed. Brady v. Maryland, 373 U. S., at 87. Even in the absence of a specific request, the prosecution has a constitutional duty to turn over exculpatory evidence that would raise a reasonable doubt about the defendant's guilt. United States v. Agurs, 427 U. S., at 112. The prosecution must also reveal the contents of plea agreements with key government witnesses, see Giglio v. United States, 405 U.S. 150 (1972), and under some circumstances may be required to disclose the identity of undercover informants who possess evidence critical to the defense, Roviaro v. United States, 353 U.S. 53 (1957).
We have, however, never squarely addressed the government's duty to take affirmative steps to preserve evidence on behalf of criminal defendants. The absence of doctrinal development in this area reflects, in part, the difficulty of developing rules to deal with evidence destroyed through prosecutorial neglect or oversight. Whenever potentially exculpatory evidence is permanently lost, courts face the treacherous task of divining the import of materials whose contents are unknown and, very often, disputed. Cf. United States v. Valenzuela-Bernal, supra, at 870. Moreover, fashioning remedies for the illegal destruction of evidence can pose troubling choices. In nondisclosure cases, a court can
One case in which we have discussed due process constraints on the Government's failure to preserve potentially exculpatory evidence is Killian v. United States, 368 U.S. 231 (1961). In Killian, the petitioner had been convicted of giving false testimony in violation of 18 U. S. C. § 1001. A key element of the Government's case was an investigatory report prepared by the Federal Bureau of Investigation. The Solicitor General conceded that, prior to petitioner's trial, the F. B. I. agents who prepared the investigatory report destroyed the preliminary notes they had made while interviewing witnesses. The petitioner argued that these notes would have been helpful to his defense and that the agents had violated the Due Process Clause by destroying this exculpatory evidence. While not denying that the notes might have contributed to the petitioner's defense, the Court ruled that their destruction did not rise to the level of constitutional violation:
In many respects the instant case is reminiscent of Killian v. United States. To the extent that respondents' breath samples came into the possession of California authorities, it was for the limited purpose of providing raw data to the
Given our precedents in this area, we cannot agree with the California Court of Appeal that the State's failure to retain breath samples for respondents constitutes a violation of the Federal Constitution. To begin with, California authorities in this case did not destroy respondents' breath samples in a calculated effort to circumvent the disclosure requirements established by Brady v. Maryland and its progeny. In failing to preserve breath samples for respondents, the officers here were acting "in good faith and in accord with their normal practice." Killian v. United States, supra, at 242. The record contains no allegation of official animus towards respondents or of a conscious effort to suppress exculpatory evidence.
More importantly, California's policy of not preserving breath samples is without constitutional defect. Whatever duty the Constitution imposes on the States to preserve evidence, that duty must be limited to evidence that might be expected to play a significant role in the suspect's defense.
Although the preservation of breath samples might conceivably have contributed to respondents' defenses, a dispassionate review of the Intoxilyzer and the California testing procedures can only lead one to conclude that the chances are extremely low that preserved samples would have been exculpatory. The accuracy of the Intoxilyzer has been reviewed and certified by the California Department of Health.
We conclude, therefore, that the Due Process Clause of the Fourteenth Amendment does not require that law enforcement agencies preserve breath samples in order to introduce the results of breath-analysis tests at trial.
It is so ordered.
JUSTICE O'CONNOR, concurring.
Rules concerning preservation of evidence are generally matters of state, not federal constitutional, law. See United States v. Augenblick, 393 U.S. 348, 352-353 (1969). The failure to preserve breath samples does not render a prosecution fundamentally unfair, and thus cannot render breath-analysis tests inadmissible as evidence against the accused. Id., at 356. Similarly, the failure to employ alternative methods of testing blood-alcohol concentrations is of no due
For a number of years, there was uncertainty whether the California courts would extend the Hitch decision to the Intoxilyzer. In People v. Miller, 52 Cal.App.3d 666, 125 Cal.Rptr. 341 (1975), a Court of Appeal panel refused to extend Hitch because the Intoxilyzer does not reduce breath samples to a preservable form comparable to the ampoules created with the device involved in Hitch. The Court of Appeal in Trombetta declined to follow Miller, and reasoned that as long as there were other methods of preserving specimens (such as the Indium Tube Kit, see n. 3, supra), the State was obliged to preserve a breath sample equivalent to the one used in the Intoxilyzer. 142 Cal. App. 3d, at 143-144, 190 Cal. Rptr., at 322-323.