Guide
Who needs a private investigator?
A private investigator can do what an online search cannot: visit courthouses that keep records only on paper, interview people and follow up in the field.
An investigator has no special access to protected records. Federal law makes it a crime to get someone's bank records (15 U.S.C. 6821) or phone records (18 U.S.C. 1039) by pretending to be them.
Most states license private investigators. Look the license up before you hire; in California, the Bureau of Security and Investigative Services licenses investigators and posts a license check.
All states
Background Checks by state
Every state page lists that state's official background check sources, each opened and verified.