How do I become a police sketch artist?

[Dale_The_Bold]

I recently lost my job and I was watching the news and there’s always some murder or (in today’s case) a guy masturbating in a woman’s apartment. So they draw up a picture based on the descriptions given by the witness(es). The thing that annoys me is that they are either too generic (fat guy with a cap looked like the police captain–without a hat), or they look like E.T. early production sketches. Okay, I could have done that well in high school and they are better than some people draw, but even the FBI has some nasty drawings of suspects. So, how does an artist such as myself lend his services to law enforcement? How do they normally do this, would I have to become an officer?