Should Mickey have gone to jail?

When Sammy shoots the man in the petrol station he knows he's in trouble, but Mickey is also taken to jail with Sammy even though he didn't do anything. Maybe it's because he ran away from the police with Sammy, but still a seven year prison sentence is way to harsh, don't you think?

If this hadn't happened and the police weren't so harsh the killing of both twins could have been prevented.