A Trombetta motion is a request asking the court to sanction the prosecution, sometimes by excluding evidence or dismissing the case, because the government failed to preserve evidence that could have helped your defense. It gets its name from the U.S. Supreme Court case California v. Trombetta.
In a DUI, this often comes up around breath testing. Unlike a blood sample, which can be re-tested later, a breath sample is usually not saved. The machine reads it and it's gone. When the defense can show the lost evidence had clear value to the case and can't be replaced by other means, a Trombetta motion argues that losing it violated your due process rights.
The standard is demanding. Courts generally require that the evidence had an apparent exculpatory value before it was destroyed, and that you couldn't get comparable evidence some other way. If police acted in bad faith by destroying evidence they knew could help you, that strengthens the argument further under a related case, Arizona v. Youngblood.
These motions don't win every time, but they can. Even when a Trombetta motion doesn't end a case, raising it can expose weaknesses in how evidence was handled and create leverage in negotiations.
This kind of technical fight is part of a thorough defense. See how Joe handles chemical evidence on the BAC defense page.
This is general information, not legal advice, and every case is different. To discuss your case for free, call (858) 622-7280 or visit /contact.