Do you think that being under the influence of a drug excuses misconduct, or in some way diminishes guilt?

It seems like every few weeks another well known celebrity is caught in some kind of public misbehavior, followed by the explanation that the famous person is suffering from a substance use disorder and will be entering a treatment program. Mel Gibson, Amy Winehouse, Drew Barrymore, Gary Busey, Britney Spears, Lindsay Lohan, Paris Hilton, and other film actors and rock stars have made public confessions of their substance abuse and have gone to expensive residential treatment programs. Whether or not these individuals or anyone for that matter will be successful in their treatment is unknown. One question that most people do have is whether the individuals blame their misbehavior on the substance rather than taking responsibility for their behavior.

Do you think that being under the influence of a drug excuses their misconduct, or in some way diminishes their guilt? If unsuccessful in treatment, what would you change in the person’s treatment?