Part of the Service

Polceman: "I'm afraid that I'm going to have to lock you up for the night."
Man: "What's the charge?"
Polceman: "Oh, there's no charge. It's all part of the service."

Material Witness

I witnessed a robbery in a fabric factory and immediately called the police. They caught the culprit and held me as a material witness.

Bad Party

A policeman pulled a blonde over after she'd been driving the wrong way on a one-way street.
Cop: Do you know where you were going?
Blonde: No, but wherever it is, it must be bad 'cause all the people were leaving.