Decided June 19, 1961.
Included here for historical interest.
Ms. Mapp was convicted of possession of pornography (gasp!) after the police made a warrantless search of her home based on a tip that there was a bad person inside (they had a piece of paper that they pretended was a warrant, and she was handcuffed because she wouldn't give it back to them). At the time, the state courts were not bound by the federal constitution, so the exclusionary rule did not apply (although most states had their own version of the exclusionary rule, apparently Ohio wasn't so forward-thinking).
The court held that the 4th Amendment (and therefore the exclusionary rule) was enforceable in state courts by way of the authority of the 14th Amendment. It's very strange the way that the Court explained this decision... as far as I can tell, earlier decisions had already held that the 4th Amendment prohibited unreasonable search and seizure by state agents just as much as they did by federal agents, but had declined to tell state courts what to do about it (so evidence illegally obtained by state agents would not be admissible in federal court, but state courts were free to make their own rules about the admissibility of such evidence). This decision doesn't really emphasize the reasoning of using the 14th Amendment to apply other constitutional guarantees to the states (it alludes to Wolf v. Colorado and Elkins v. US for that). Instead, this decision takes a few pages to say "we've let the state courts do it their way and it hasn't worked, so now they'll have to do it our way for reasons we've already explained."
Anyway, the evidence (four pamphlets, two photographs, and "a little pencil doodle") was suppressed.