Can police search your phone?

In Riley v. California in 2014, a unanimous Supreme Court held that police generally need a warrant to search the contents of a cell phone seized during an arrest. The reasoning was that phones contain a quantity and quality of personal information without precedent in physical objects, so the traditional rule allowing search of items on an arrestee does not extend to them. Police may seize the phone and secure it while seeking a warrant, and exigent circumstances such as an imminent threat can still justify a warrantless search in narrow cases, but the default is a warrant.

Consent remains the most common way phones get searched. If you unlock the phone and hand it over, or agree when asked, no warrant is needed and the search is lawful. You are not required to consent, and declining cannot itself be used as evidence of guilt. If you do not want a search, say clearly that you do not consent, and do not physically resist. Border crossings are a significant exception, where customs officers have broader authority to inspect devices without a warrant under the border search doctrine, though courts have begun to require reasonable suspicion for forensic searches in some circuits.

Compelled unlocking is where the law is genuinely unsettled. Several courts have held that forcing someone to state a passcode is testimonial and protected by the Fifth Amendment, while compelling a fingerprint or face scan is not, on the theory that biometrics are physical characteristics like a blood sample. Other courts have disagreed on both points, and the Supreme Court has not resolved it. Practically, that is why civil liberties groups advise disabling biometric unlock in situations where a search is a concern, using a strong passcode, and knowing that most phones require the passcode after a restart.