American courts have thrown out evidence in some of the most consequential criminal cases on record, and the famous cases where evidence was excluded are the ones that built the rules police and prosecutors follow today. The list below runs from the 1914 decision that first told federal agents they couldn’t use what they seized illegally, through modern rulings on cell phones and location data, and includes two celebrity trials where the problem wasn’t the law but the way the state gathered its proof.
Weeks v. United States (1914)
Fremont Weeks was arrested for mailing lottery tickets. While he was in custody, a U.S. Marshal entered his home without a search warrant, went through his room, and carried away letters and personal papers. Weeks asked the court to give the property back, arguing the seizure violated the Fourth Amendment.
The Supreme Court agreed and reversed his conviction, holding that evidence obtained by federal officers in violation of the Fourth Amendment cannot be used in federal court. Allowing illegally seized evidence, the Court reasoned, would make the Fourth Amendment meaningless because police could simply ignore it and rely on the courts to admit the results anyway. That decision created what lawyers now call the exclusionary rule.1Justia U.S. Supreme Court Center. Weeks v. United States, 232 U.S. 383 (1914)
The rule only bound federal agents. State and local police operated under no such restriction for another 47 years.
Mapp v. Ohio (1961)
On May 23, 1957, Cleveland police showed up at Dollree Mapp’s home looking for a bombing suspect and gambling materials. When Mapp refused to let them in without a warrant, officers forced open her door. They found neither the suspect nor gambling paraphernalia, but they did find materials they deemed obscene, which was enough for an arrest under Ohio law at the time. No search warrant was ever produced at trial.2Justia U.S. Supreme Court Center. Mapp v. Ohio, 367 U.S. 643 (1961)
The Supreme Court overturned Mapp’s conviction 5–4 and ruled that “all evidence obtained by searches and seizures in violation of the Constitution is inadmissible in a state court.” The exclusionary rule now bound every police department and prosecutor’s office in the country.2Justia U.S. Supreme Court Center. Mapp v. Ohio, 367 U.S. 643 (1961)
Wong Sun v. United States (1963)
Federal narcotics agents in San Francisco arrested James Wah Toy at his laundry on a tip that fell well short of probable cause. During the arrest, Toy named Johnny Yee, who surrendered a quantity of heroin. Yee pointed to a third man, Wong Sun. Toy and Wong Sun were convicted on the strength of Toy’s statements, the heroin, and later pretrial statements.
The Supreme Court held that Toy’s arrest was illegal, and everything that flowed from it was tainted. Toy’s statements in his bedroom moments after agents broke in were suppressed as direct products of the unlawful entry. The heroin Yee surrendered was thrown out too, because agents never would have found Yee without Toy’s coerced statements. The Court described this as “verbal evidence which derives so immediately from an unlawful entry and an unauthorized arrest” that it stood on the same footing as physical evidence taken in an illegal search.3Library of Congress. Wong Sun v. United States, 371 U.S. 471 (1963)
The case gave force to the fruit of the poisonous tree doctrine. When the initial police action is illegal, evidence that grows out of it is equally inadmissible. An officer who illegally searches a car and finds a storage locker key loses both the key and whatever the locker holds.4LII / Legal Information Institute. Fruit of the Poisonous Tree
Miranda v. Arizona (1966)
Ernesto Miranda was arrested at his home in Phoenix and taken to a police station, where two officers interrogated him for two hours. He signed a written confession that prosecutors used to convict him of kidnapping and rape. No one told him he had the right to remain silent or the right to a lawyer.5United States Courts. Facts and Case Summary – Miranda v. Arizona
The Supreme Court threw out the confession. Before any custodial interrogation, police now had to inform suspects of the right to remain silent and the right to have an attorney present. Statements taken without those warnings are generally inadmissible, and once a suspect invokes either right, questioning must stop.
Miranda himself was retried on other evidence, convicted again, and sent to prison.
There is a notable carveout. In New York v. Quarles (1984), the Court recognized a public safety exception. Officers can ask questions without Miranda warnings when there is an immediate threat, such as locating a discarded weapon in a public place, and statements obtained under those circumstances remain admissible.
Katz v. United States (1967)
Charles Katz was convicted of illegal gambling based on phone conversations the FBI recorded by attaching a listening device to the outside of a public phone booth. The government argued that because no one physically entered the booth, there was no search. The Supreme Court disagreed and held that the Fourth Amendment “protects people, not places.”6Justia U.S. Supreme Court Center. Katz v. United States, 389 U.S. 347 (1967)
Justice Harlan’s concurrence produced the two-part test still used today: the person must have shown an actual expectation of privacy, and that expectation must be one society recognizes as reasonable. Katz closed the door and paid for the call, which met both parts. Because the wiretap was warrantless, the recordings were suppressed.7LII / Legal Information Institute. Expectation of Privacy
Riley v. California (2014) and Carpenter v. United States (2018)
Two modern rulings pulled the Fourth Amendment into the digital era, and both ended with evidence thrown out.
In Riley, police arrested David Riley for a traffic violation, searched his smartphone without a warrant, and found photos and messages linking him to a gang shooting. The Supreme Court held unanimously that police generally cannot search the digital contents of a cell phone seized during an arrest without first getting a warrant. A phone, the Court said, contains far more private information than anything a person carries in a pocket.8Justia U.S. Supreme Court Center. Riley v. California, 573 U.S. 373 (2014)
In Carpenter, prosecutors investigating a string of armed robberies obtained 127 days of Timothy Carpenter’s cell-site location data, amounting to 12,898 location points. They used a court order that required only “reasonable grounds” rather than the probable cause a warrant demands. The Supreme Court ruled that acquiring that volume of location data is a Fourth Amendment search and requires a warrant supported by probable cause. Historical cell-site records, the Court noted, let the government “travel back in time to retrace a person’s whereabouts.”9Justia U.S. Supreme Court Center. Carpenter v. United States, 585 U.S. ___ (2018)
The O.J. Simpson Trial (1995)
The 1995 murder trial of O.J. Simpson showed how sloppy evidence handling can undermine powerful forensic proof. DNA testing linked Simpson’s blood to drops found near the bodies of Nicole Brown Simpson and Ron Goldman, with experts testifying the odds of a random match were one in 170 million.
The defense didn’t challenge whether DNA testing worked. It attacked how investigators collected and stored the evidence. A single swab had been used to collect multiple bloodstains, samples were stored improperly, and documentation of who handled what and when had gaps. Barry Scheck later summarized the approach: “We had a 21st century technology and 19th century evidence collection methods.”
Every piece of physical evidence carries a chain of custody, a record of every person who has handled it from collection through trial. Prosecutors must show the evidence is the same material collected at the scene and hasn’t been contaminated or tampered with.10National Institute of Justice. Chain of Custody of Evidence
The jury did not formally suppress the DNA evidence, but the defense’s contamination arguments created enough doubt to contribute to an acquittal. Crime labs and police departments across the country revised how they collect and store forensic evidence in the years that followed.
Bill Cosby (2021)
Bill Cosby’s 2018 sexual assault conviction was thrown out three years later by the Pennsylvania Supreme Court on grounds that had nothing to do with whether he committed the crime. The issue was how prosecutors got the evidence.
In 2005, a district attorney publicly declined to charge Cosby, citing insufficient evidence. Relying on that assurance, Cosby gave testimony in a civil lawsuit brought by his accuser, Andrea Constand, and made damaging admissions in the deposition because he believed he could not be prosecuted. A different prosecutor later used those admissions to bring criminal charges and secure a conviction.
The Pennsylvania Supreme Court held that using the deposition testimony against Cosby violated his due process rights. He had spoken only because a prosecutor’s public commitment made him believe the statements could never be used in a criminal case. When a later prosecutor broke that implicit promise, the evidence was tainted. The U.S. Supreme Court declined to review the ruling, and Cosby was released from prison.
When Courts Let Evidence Stay
Not every police mistake ends with evidence thrown out. Courts have carved several exceptions into the exclusionary rule so that clearly guilty defendants don’t walk free over minor errors.
- Good faith. If officers reasonably believed they were acting lawfully, the evidence may survive even when the legal authority behind their search turns out to be defective. United States v. Leon (1984) established the rule in a case where officers relied on a warrant that was later found invalid. The Court reasoned that excluding the evidence would not deter future misconduct because the officers had relied in good faith on a judge’s approval.11LII / Legal Information Institute. Good Faith Exception to Exclusionary Rule
- Inevitable discovery. Evidence stays in if prosecutors can show police would have found it through lawful means anyway. In Nix v. Williams (1984), the Court allowed a murder victim’s body into evidence because a search party was already within two and a half miles of the location and moving toward it, and would have found the body that day regardless of the officer’s misconduct.12LII / Legal Information Institute. Inevitable Discovery Rule
- Plain view. Officers lawfully present in a location can seize evidence of a crime that is in plain sight without a warrant. The officer must have a lawful right to be where they are when they spot the evidence; an officer who entered a home illegally cannot invoke the doctrine for anything found inside.13LII / Legal Information Institute. Plain View Doctrine
- Public safety. Under Quarles, statements given in response to questions about an immediate public safety threat remain admissible even without Miranda warnings.
How Evidence Actually Gets Thrown Out
A defendant who believes evidence was obtained illegally files a motion to suppress, asking the judge to rule the evidence inadmissible before trial.14LII / Legal Information Institute. Motion to Suppress The defense identifies the evidence and the constitutional right or rule that was violated. The judge holds a hearing, listens to both sides, and decides whether to exclude.
A successful motion can reshape the case. Without a key confession or a critical piece of physical evidence, prosecutors sometimes lack enough to go forward, and the result may be reduced charges, a better plea offer, or outright dismissal. Miranda’s own story shows the other possibility: his confession was thrown out, but the state retried him on other evidence and won a second conviction.