Mischa Barton sitting in front rowHugo by Hugo Boss Fashion Show at Westhafen Mercedes-Benz Fashion Week Spring Summer 2009, Berlin, Germany - 17.07.08

The former The O.C. star was arrested on suspicion of DUI in December, and was sentenced to 36 months on probation, alcohol education classes and a fine after pleading guilty to charges this spring (Apr08).

And now Barton has revealed she punished herself over the lapse in judgment by locking herself up at an unnamed rehab clinic in a bid to prove to herself and the authorities she was not a drunk.

She tells Marie Claire's UK edition, "I wanted to prove to the court that I would take it completely seriously, so I went to rehab to prove I was sober.

"It really helped in getting the more serious aspects of my case dropped because, you know, that's what they want to hear; you're not an alcoholic and you don't have a problem. So I did it in the most low-key way possible - I didn't make a fuss about it and I didn't tell a lot of my friends. I just did the program and got through it."

And she's still angry with herself for driving while over the limit.

She adds, "The thing is, I hate drunk drivers. Living in L.A., I can't stand them, and that's why I was so disappointed in myself. It's so not worth it when you put other lives at risk."

Source: WENN