Short answer
The prosecution generally can’t use the suppressed evidence in its main case at trial, and evidence derived from it may be excluded too. But the case doesn’t automatically end. The prosecution may go forward with other evidence or dismiss, the government may be able to appeal, and suppressed evidence can sometimes be used to impeach a defendant who testifies.
What gets excluded
Suppression keeps evidence out of the prosecution’s “case in chief,” the evidence it offers to prove guilt (the phrase the Supreme Court used in United States v. Leon). It can also reach evidence obtained by exploiting the violation. See fruit of the poisonous tree. A court may grant a motion in part, suppressing some evidence and admitting the rest.
What the prosecution can do next
- Go forward with whatever admissible evidence remains.
- Dismiss the charges if the remaining evidence isn’t enough.
- Appeal. In federal court, “An appeal by the United States shall lie to a court of appeals from a decision or order of a district court suppressing or excluding evidence” if it’s made before jeopardy attaches and the U.S. attorney certifies “that the appeal is not taken for purpose of delay and that the evidence is a substantial proof of a fact material in the proceeding.” The appeal must be taken within thirty days (18 U.S.C. § 3731). States have their own rules on prosecution appeals.
The impeachment exception
Suppressed evidence isn’t always gone for good. In Walder v. United States (1954), a defendant testified that he had never possessed narcotics. The Supreme Court held that this “opened the door, solely for the purpose of attacking petitioner’s credibility,” to evidence that had been unlawfully seized.
In United States v. Havens (1980), the Court extended this to answers on cross-examination: statements “made in response to proper cross-examination reasonably suggested by the defendant’s direct examination are subject to otherwise proper impeachment by the Government, albeit by evidence that has been illegally obtained and is inadmissible as substantive evidence of guilt.” Whether to testify is a decision to make with counsel.
In an ALPR case
A successful challenge often doesn’t suppress the camera record itself. It suppresses what officers found because of an unlawful stop or search. See grounds to suppress ALPR evidence. Some states also have statutes making ALPR evidence inadmissible when the statute is violated. See the state law comparison. Even when evidence comes in, questions like who was driving remain for trial.
Law varies by state. State constitutions, statutes and courts may treat this issue differently from federal law. A licensed attorney in your jurisdiction can tell you how it applies.
Sources
- OpinionUnited States v. Leon468 U.S. 897 (1984)
- OpinionWong Sun v. United States371 U.S. 471 (1963)
- Statute18 U.S.C. § 3731, “Appeal by United States”Accessed 2026-11-05
- OpinionWalder v. United States347 U.S. 62 (1954)
- OpinionUnited States v. Havens446 U.S. 620 (1980)
Related
- Fruit of the Poisonous TreeThe fruit of the poisonous tree doctrine explained: Wong Sun's exploitation test, how a chain forms after an ALPR alert or data search, and where courts say it breaks.
- What Happens at a Suppression HearingHow suppression hearings work: filing deadlines, testimony, the burden of proof, Franks hearings, defendant testimony, and the ALPR records a judge may examine.
- Grounds to Suppress ALPR EvidenceThe grounds for a motion to suppress license plate reader evidence: unverified alert stops, warrantless searches of stored data, defective warrants, and their fruits.