(people.com) - Mischa Barton was sentenced to three years of unsupervised probation in a Beverly Hills courtroom Thursday in her DUI case. The former O.C. star pleaded no contest to drunken driving in a plea deal reached with prosecutors and which will spare her jail time. In addition, a marijuana possession charge against Barton was dropped (due to the small amount found, a source told to PEOPLE). Another charge of driving without a license was reduced to an infraction. The actress did not attend the hearing. Her attorney, Anthony V. Salerno, was there on her behalf. "The DAs were very fair in handling this case," Salerno said outside the courtroom. "Mischa's glad the case has been resolved."Barton, 22, was ordered to complete a three-month alcohol-education class and pay a fine of approximately $2,000. Legal experts say such a deal is common for first-time offenders. In a statement released after the hearing, her lawyer added: "Ms. Barton understands the seriousness of this situation and assumes full responsibility for her actions. She and I are grateful to the Court and the District Attorney's Office for the prompt and respectful resolution of the case." The actress was arrested for DUI in Los Angeles on Dec. 27, after sheriff deputies spotted her weaving between two lanes of traffic and she failed to signal when making a turn. On Jan. 10, Barton said on Ryan Seacrest's KIIS-F.M. radio show: "Obviously I'm 100 percent responsible for my actions in this case. I'm really disappointed in myself. I don't know what to say about it, except that I'm not perfect, and I just don't ever intend to do something this stupid again."