i cant and wont take a lecture on law (something i studied for long enough for two years) from someone with the name "pimpdollar".
If your a witness to a crime, you make yourself known to the police, they take your details and a quick statement. they then contact you and ask you to come to the station if the case continues. they dont arrest you. ever
They way it sounds, Jack has been arrested for being an acomplise (spelling) if he knew the person involved and there for the police take a view on it as he played an active role in the incident.
I have witnessed a car crash, an assault and a arson attack over the last few years and have never once been arrested just to back up my point.