Because driving with a busted taillight is illegal? I've had a similar situation where I had an electrical problem and the taillights were out in my car. (Brake

Because driving with a busted taillight is illegal? I've had a similar situation where I had an electrical problem and the taillights were out in my car. (Brake lights still worked). Got pulled over and cited for driving without insurance. The original investigation into a minor traffic violation escalated to a bigger infraction, and a bigger fine. It's a very common police tactic to start with a minor infraction then investigate to find any further violations. This isn't wrong, and is actually good police work. But it can be easy to abuse if applied with a racial bias, or some other prejudice. (And which is why independent police oversight is a necessity. Not just for high-profile killings, but also for monitoring how law enforcement operates in the community in small ways).