What USCIS Checks
FBI database: criminal record, federal crimes, warrants. State police records: state crimes, arrests. INTERPOL: international crimes. They check if you're under investigation anywhere. They verify your immigration history—are you lying about when you entered the US?
The Timeline
Initial background check: 2-4 weeks after you submit N-400. If red flags appear: additional investigation (can add months). If cleared: you proceed to interview. Most people pass (95% pass rate).
What Fails You
Felony conviction (usually permanent bar). Drug-related crimes (most create bars). Crimes of violence. Fraud or immigration fraud (if you lied on Green Card application). Gang membership or terrorism links. These are serious barriers.
How to Prepare
Be honest on N-400. If you have a record: get legal advice before applying. USCIS will find out anyway—lying makes it worse. If you're in the system for other reasons (lawsuit, etc.), disclose it.