It's not unusual for Dally to be in the cooler. Which is right where he is now. He's currently in for beating the fuck out of a kid who insulted his friend, Johnny. The police officer leads Dally to a prison cell, where he'll serve a sentence of six months.

Officer: "If I were you, I'd be a good boy from now on. Your record's getting crowded."

In response to this, Dally just rolls his eyes. The officer shoves Dally into the cell after unlocking the handcuffs around his wrist, and then closes the cell and walking away.