The 61-year-old actress -- who entered her plea through her attorney -- was immediately sentenced to three years probation and ordered to undergo a nine-month alcohol program, according to Jane Robison of the District Attorney's Office.
DeWitt must also pay a $510 fine, plus penalty assessments, according to Robison, who said a second misdemeanor DUI count was dismissed as a result of her plea.
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El Segundo police Sgt. Danny Kim said at the time of DeWitt's arrest that an officer saw her drive past a barricade intended to control vehicular traffic near a park in the vicinity of Pine Avenue and Sierra Street.
"As the officer spoke with DeWitt, he observed signs and symptoms of alcohol intoxication," Kim said.
After a series of field sobriety tests, the actress was arrested and transported to the El Segundo Police Department for booking. She was released early the next morning on $5,000 bail.
DeWitt portrayed Janet Wood on the television series, "Three's Company," which ran from 1977-1984 and also starred John Ritter and Suzanne Somers.