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U.S. Supreme Court
CALIFORNIA v. TROMBETTA, 467 U.S. 479 (1984)

No. 83-305.
Argued April 18, 1984
Decided June 11, 1984

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. Page 481 Maryland, 373 U.S. 83 (1963). This case raises the question whether the Fourteenth Amendment also demands that the State preserve potentially exculpatory evidence on behalf of defendants. In particular, the question presented is whether the Due Process Clause requires law enforcement agencies to preserve breath samples of suspected drunken drivers in order for the results of breath-analysis tests to be admissible in criminal prosecutions.

  1. 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.[fn1] The Intoxilyzer analyzes the suspect's breath. To operate the device, law enforcement officers follow these procedures:

    "Prior to any test, the device is purged by pumping clean air through it until readings of 0.00 are obtained. The breath test requires a sample of `alveolar' (deep lung) air; to assure that such a sample is obtained, the subject is required to blow air into the intoxilyzer at a constant pressure for a period of several seconds. A breath sample is captured in the intoxilyzer's chamber and infrared light is used to sense the alcohol level. Two samples are taken, and the result of each is indicated on a printout card. The two tests must register within 0.02 of each other in order to be admissible in court. After each test, the chamber is purged with clean air and then Page 482 checked for a reading of zero alcohol. The machine is calibrated weekly, and the calibration results, as well as a portion of the calibration samples, are available to the defendant." 142 Cal.App.3d 138, 141-142, 190 Cal.Rptr. 319, 321 (1983) (citations omitted).

    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.[fn2] Each respondent registered a blood-alcohol concentration substantially higher than 0.10 percent. Under California law at that time, drivers with higher than 0.10 percent blood-alcohol concentrations were presumed to be intoxicated. Cal. Veh. Code Ann. § 23126(a)(3) (West 1971) (amended 1981). Respondents were all charged with driving while intoxicated in violation of Cal. Veh. Code Ann. § 23102 (West 1971) (amended 1981).

    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,[fn3] California law enforcement officers Page 483 do not ordinarily preserve breath samples, and made no effort to do so in these cases. Respondents each claimed that, had a breath sample been preserved, he would have been able to impeach the incriminating Intoxilyzer results. All of respondents' motions to suppress were denied. Respondents Ward and Berry then submitted their cases on the police records and were convicted. Ward and Berry subsequently petitioned the California Court of Appeal for writs of habeas corpus. Respondents Trombetta and Cox did not submit to trial. They sought direct appeal from the Municipal Court orders, and their appeals were eventually transferred to the Court of Appeal to be consolidated with the Ward and Berry petitions.[fn4]

    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 Page 484 systematic procedures to preserve the captured evidence or its equivalent for the use of the defendant." 142 Cal.App.3d, at 144, 190 Cal.Rptr., at 323.[fn5] The court granted respondents Ward and Berry new trials, and ordered that the Intoxilyzer results not be admitted as evidence against the other two respondents. The State unsuccessfully petitioned for certiorari in the California Supreme Court, and then petitioned for review in this Court. We granted certiorari, 464 U.S. 1037 (1984), and now reverse. Page 485