Source: https://www.losangelesduiattorney.com/glossary/california-v-trombetta/
Timestamp: 2019-04-23 00:43:34+00:00

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California v. Trombetta was a Supreme Court case that found that police do not have to preserve DUI breath test samples like other evidence. It was also be used as a precedent along with a later case, Arizona v. Youngblood, to establish rules for destroyed or missing evidence.
In a DUI case (or any criminal case), a defendant normally has a right to examine or test the evidence that the prosecution is using against them. So, for example, a blood sample used in a DUI drug test can be “split” so that the accused driver can have an independent lab test it. Similarly, the defendant can request a copy of videos, witness statements, or other documents that may be used against them. As a driver accused of DUI, this is part of your Constitutional right to due process and a fair trial.
With DUI breath tests, however, these rules create a problem: once the suspect blows into the breath test device, the breath is gone. It cannot be captured, saved, or “re-tested” later. This issue is at the heart of an important Supreme Court case, California v. Trombetta, that found that breath test samples do not have to be saved like other evidence.
What was the California v. Trombetta case all about?
California v. Trombetta actually started as four separate California DUI cases. Between 1980 and 1981, four different drivers arrested for DUI in California all had the same complaint: breath test evidence was used against them in their case, but there was no way for them to independently test the breath samples to see if the tests were accurate. Their initial motions to exclude the breath test evidence were all denied.
These four defendants grouped their cases together and appealed to the California Court of Appeals. This court initially granted them a new trial, ordering that the breath test results be excluded. This sparked a legal battle, however, and the case ended up going all the way to the United States Supreme Court. The case became named after one of the defendants, whose last name was Trombetta.
The “evidence” in a DUI case is not the physical breath itself, but the data about its alcohol content that is gathered by the machine. As long as the data is available, the evidence has been preserved. This was, essentially, the Supreme Court’s way of addressing the fact that it is physically impossible to save a breath sample.
The second reason is more of a legal argument. The court said that allowing the breath sample to dissipate doesn’t violate due process or cause an unfair trial, because breath test evidence doesn’t have much value in clearing a defendant’s name. It is not going to be a “smoking gun,” so to speak, that proves the defendant was sober—and there are other ways for the defendant to prove that. Thus, there is nothing really unfair about letting the breath sample disappear.
How does the Trombetta decision affect my DUI case?
California v. Trombetta was not a win for DUI defendants. But it did help establish the rules around how DUI breath tests can be challenged in court. Most importantly, because it is the validity of the data that is the “evidence,” and not the breath itself, any challenge to the accuracy of the test can get that test thrown out, regardless of how high the result was. This has even called into question how reliable breath tests are as a whole, so much so that there are detailed rules for how they must be calibrated and administered. If any rule was broken, it can help your case.
Trombetta was also used as a precedent in a later case, Arizona v. Youngblood, which set rules for other types of missing or destroyed evidence. Because of these cases, you could use a request known as a Trombetta-Youngblood motion to get your DUI case dismissed entirely.

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