Depending upon the circumstances of an altercation, law enforcement for their protection and your son's protection may be within its rights to have used the force that was used in retsraining your son even though he was handcuffed to a bed.You need to read the police and incident report carefully to see law enforcement's version of what transpired and compare the the written documents with your son's version.If in fact your 18 year old son was actually drinking alcohol and engaging in disorderly conduct, his ability to recall the events which actually happened with law enforcement may be slightly off due to the fact tha alcohol ingestion affects one's ability to recall events.