California v. Trombetta

Background

Four people stopped on suspicion of drunk driving in California submitted to breath tests on an Intoxilyzer and registered blood-alcohol levels above California’s legal threshold. The officers did not preserve the breath samples. The drivers asked courts to block the breath-test results because saved samples would let them seek independent retesting or challenge the machine’s accuracy. A California court agreed and excluded the test results or ordered new trials for the drivers.

Reasoning

The Supreme Court reviewed whether the Fourteenth Amendment’s promise of fair process requires police to save breath samples. The Court explained that defendants already have a right to get evidence that is clearly helpful to guilt or punishment, but the Constitution does not force police to preserve every kind of raw material. The Justices applied a two-part practical test: evidence must have apparent exculpatory value before it’s lost and be unavailable by other reasonable means. The Court found Intoxilyzer testing generally reliable, officers acted in good faith, and defendants had alternatives like inspecting calibration records or choosing blood or urine tests that are preserved.

Real world impact

The ruling means police may use breath-analysis results at trial even when they did not save the breath sample, unless a case shows the lost sample clearly would have been exculpatory and could not be obtained otherwise. States remain free to set stricter rules, including requiring preservation or informing suspects about testing options, but the federal Constitution does not impose that duty.

Dissents or concurrances

A concurring opinion emphasized that preservation rules are generally matters for state law and agreed that failing to save breath samples does not by itself make a prosecution unfair under the Federal Constitution.