In 2003, a man broke into the victim's house and raped her. Police were unable to determine the man's identity from the woman's description, but police were able to get the man's DNA. In 2009, Alonzo King was arrested for an unrelated assault. During booking, as was standard practice for serious offenses under Maryland law, the police used a cotton swab to take a DNA sample from the inside of King's cheek. The DNA was run through a law enforcement database, and officers found that it matched the DNA of the perpetrator from the 2003 rape. The state court admitted the DNA evidence and convicted King of the rape. The Court of Appeals of Maryland reversed, holding that the cotton-swab procedure constituted an unreasonable search and seizure under the Fourth Amendment. The United States Supreme Court granted certiorari.