Factual error: In a shot in Harlem, a Ford Econoline AVIS rental truck drives on the adjacent street. The specific Econoline van was at least a mid-90's to 2000+ model van and the movie takes place in the 70s.
Factual error: The ambulance that the junkie cop leaps out of is a mid-1980s GMC (note the 4 square headlamps), though the film takes place in 1971. (00:35:55)
Factual error: At one point, Frank Lucas is speaking on a public telephone. Visible in the background is a poster with a web address on it (ends in .biz).
Factual error: As the camera is following behind the red Bronco, at the right side of the screen a modern, white NYPD Chevy Malibu is briefly seen. (01:01:40)
Factual error: When Frank puts coins in the pay phone, a blue label states it is a NYNEX phone. It is 1970, yet NYNEX wasn't formed until 1984. (00:20:45)
Revealing mistake: When the cops bust the lab where the dope is cut they push a big man in a white T-shirt. The blood pack on his back is very noticeable.
Answer: The idea is if cops wouldn't take a million dollars for themselves, free and clear without risk, they are impeccably honest. Therefore, they wouldn't accept bribes and probably not hold still for shakedowns or payoffs. They wouldn't cover up drug or weapon planting and would testify against crooked cops.