Mischa Barton promotes her new teen comedy, Assassination of a High School President, at the 2008 Sundance Film Festival in Park City, Utah on Monday. She arrived last night at Salt Lake City airport.

Assassination takes place at a Catholic high school, where the popular girl (Barton) teams up with a sophomore newspaper reporter to investigate a case of stolen SAT exams. Once the duo target their suspects, a larger conspiracy is unearthed. The film is scheduled for an August 2008 release.

Other pictures include: Mischa’s mom Nuala and Mischa’s costars Reece Thompson and Brett Simon.

40+ pictures inside of Mischa promoting Assassination… More Here! »

Mischa Barton arrives at Salt Lake City airport on Sunday to attend the 2008 Sundance Film Festival in Park City, Utah. She will be promoting Assassination of a High School President, her new teen comedy about stolen SAT exams.

Earlier this month, the 21-year-old former O.C. actress was spotted leaving “The Good Shepherd Catholic Church” in Beverly Hills to attend confessional. She was recently arrested for DUI, possession of illegal narcotics and driving without a valid license.

According to E!, Mischa has hired publicists Howard Bragman and Lisa Perkins of L.A.-based Fifteen Minutes, and attorney Anthony V. Salerno to be her legal counsel. (Bragman, an openly gay publicist, was hired by Isaiah Washington to handle damage control for using the F-word.)

Mischa was also recently photographed walking her two dogs, Ziggy and Charlie, in a Beverly Hills park.

15+ pictures inside of Mischa Barton @ 2008’s Sundance Film Festival… More Here! »

Mischa Barton is still on track to ring in the new year at the Luxor’s new CatHouse club next Monday, according to OK!

“We are aware of Mischa Barton’s incident last night,” a club rep said. “But at present she is still expected to host the CatHouse Grand Opening at Luxor Las Vegas on Dec. 29.”

The 21-year-old former O.C. actress was released from jail yesterday following her arrest early Thursday morning. TMZ reports that Mischa was in possession of prescription drugs (that weren’t hers), smoked marijuana that day (which cops found) and scored a .12 on her breathalyzer test. Busted!

An embarrassed Mischa Barton keeps well-hidden as leaves the the West Hollywood Sheriff’s station at 10:10AM PST in the back seat of her parents’ Mercedes.

Video at TMZ. Marissa Cooper would have at least waved to paparazzi!

Earlier this morning, the former O.C. actress was arrested for DUI, possession of illegal narcotics and driving with a suspended license. Peep Mischa’s beautiful mug shot here!

YIKES!

Mischa Barton looks absolutely dreadful in her mug shot!

Earlier today, the former O.C. actress was arrested around 3AM for DUI, possession of illegal narcotics and driving with a suspended license.

Mischa, 21, “was seen straddling two lanes of traffic and failed to signal when making a turn.”

Odds are Keds will not be renewing her as a spokesperson for 2008.

Mischa Barton was arrested for DUI early Thursday morning, reports gossip blog Hollyscoop.

The former O.C. actress was handcuffed on the corner of La Cienega and Santa Monica Blvd. in in West Hollywood, Calif. and taken into a police station at 3AM.

Mischa, 21, was driving a white Range Rover with a suspended license. She’s still in custody right now, being held on $10,000 bail.

UPDATE: Mischa reportedly was in possession of illegal narcotics at the time of the arrest. Surprise, surprise!

ARE YOU SURPRISED that yet another Hollywood starlet was caught driving under the influence?

Mischa Barton promotes her new drama romance Closing the Ring at The Late Late Show in Dublin, Ireland on Friday.

The 21-year-old former O.C. actress plays the young, lively, and optimistic Ethel Ann, who falls in love with a young farmer, Teddy Gordon (played by Canadian new comer Stephen Amell).

Later in the evening, the 21-year-old former O.C. actress and her mother, Nuala, partied at Krystle nightclub.

Closing the Ring opens in UK theaters next Friday, Dec. 28. More Here! »

Mischa Barton of The O.C. fame poses for Maxim Magazine in its January 2008 issue.

Mischa has a number of upcoming projects including Walled In, a movie adaptation of the novel Less Emmures by French writer Serge Brussolo.

Visit Maxim Online for more updates and pictures of Mischa.