Utah v. Strieff, a June 2016 decision by the U.S. Supreme Court, involved an officer stopping a man and then learning that the man had an outstanding arrest warrant. (579 U. S. ____ (2016).) The officer arrested the man and searched him as part of the arrest, finding incriminating evidence. The Court held that the evidence was admissible in court—even if the officer initially didn’t have a legitimate reason for the stop—because the existence of the arrest warrant “attenuated” the connection between the evidence and the illegal stop that led to it.
For much more on the case, including what it means for people who have outstanding warrants, see this article on the “attenuation doctrine.”