Definition of usual suspects in US English:

usual suspects

noun

  • With the. The people habitually suspected, detained, or arrested in response to a crime, especially regarded as scapegoats rather than plausible perpetrators. Hence: those people, ideas, etc., that would be expected in a particular context.

Origin

1940s. From usual + the plural of suspect, originally in the phrase round up the usual suspects spoken by Captain Louis Renault, the French prefect of police, played by Claude Rains in the 1942 U.S. film Casablanca.