Friday afternoon, Cassandra Jones was ushered into a tiny holding cell in the Alexandria courthouse to serve a 3 1/2-hour sentence. She was still there yesterday morning -- after 69 hours with no food or bed -- because a sheriff's deputy forgot about her.

Sheriff's Department officials said Jones, a 25-year-old Prince George's County resident who pleaded guilty to a misdemeanor in Alexandria's General District Court, was found sitting on a wooden bench by a deputy conducting a routine check of the courthouse.

"My whole family didn't know if I was alive or dead," said Jones, a cashier for Giant Food. "I broke the heel of my shoe banging on the window . . . . I was banging from Friday until Sunday, when I passed out."

Officials said the 8-by-11-foot room contained the bench, a light, a water fountain and a toilet, but Jones said the water fountain was not working and she had to drink from the toilet.

After she was found yesterday at 8:30 a.m., she was taken to Alexandria Hospital where she was fed intravenously and released.

"I feel very badly that it happened. I'm embarrassed," said Sheriff James H. Dunning, who was working Sunday in his third-floor office while Jones was sitting in the second-floor cell attached to courtroom No. 2. "This place is shut down on the weekends . . . . Nobody could have heard her."

One deputy is usually assigned to each prisoner and is responsible for checking that prisoner in and out of the cell. Dunning said he had suspended Deputy Vernell Bolton, ordered an investigation into the matter and would reassign and retrain some members of the staff. He said Bolton apparently forgot about Jones and left for the weekend without releasing her. He also said he did not understand why the deputy who checks the building each evening did not find her.

"It's a very graphic example of an error of complacency that has to the present existed among some personnel in the office in regard to security matters," said Dunning, who was elected last year on a pledge to improve management of the Sheriff's Department. "Maybe because we've been lucky we've been lulled into a false sense of security."

"I would have gone crazy," Jones' attorney, Christopher P. Schewe, said yesterday when he heard about his client's unexpected confinement. "She was told she would get out at 3 p.m. on Friday, and nobody said 'boo' to her over the weekend."

On Sunday, Jones' mother called the Alexandria Police Department to report that her daughter was missing, said police spokeswoman Lucy Crockett. "They checked Alexandria jail, Fairfax and Arlington, but she wasn't there."

Jones, who was arrested Feb. 13 on a charge of impeding a police officer who was investigating a domestic argument at 214 Payne St., said she was entering the house of her brother's girlfriend when a police officer pushed her aside. "My brother and his girlfriend got in a fight and I was just walking in the door . . . and all this started."

"I recommended one day in jail," said Assistant Commonwealth's Attorney Trudi A. Berlin, who had prosecuted Jones' case. "It was a clear case of impeding, but I felt it wasn't the most serious case."

"It was human error," Eric P. Geiger, a supervisor in the sheriff's operations division, said of Jones' confinement. "Some mistakes are small and some are whoppers . . . . This was a whopper."