An out-of-court settlement was reached yesterday in a $6 million lawsuit filed against Alexandria Sheriff James H. Dunning by a Prince George's County woman who was inadvertently locked in a holding cell for a weekend last year without food and water.

Both sides declined to say how much money Cassandra Jones, 26, of Fort Washington will receive in the settlement, which was agreed on just after a jury was selected for the first day of trial in federal court in Alexandria.

"I'm happy," said Jones, who had sued for violation of her civil and constitutional rights, false imprisonment, negligence and intentional infliction of emotional distress. She was pregnant at the time she was left in the cell.

"I'm very pleased," said Dunning. "Mrs. Jones has been compensated. She deserves to be compensated . . . . I think {the amount} is very fair . . . . It's a shame it wasn't accepted five months ago."

Dunning and his attorney, James Hopper, said that, apart from an additional payment to cover Jones' legal fees, she accepted "basically the same amount" offered before she filed suit in February.

"That's not true," said Jones' lawyer, Amy R. Goldson. " . . . We were prepared to go to trial today. If it was the same amount, I wouldn't have done all that work."

The settlement will be paid by the state's liability fund for sheriffs. That fund allows for a maximum of $500,000 to be paid out each year in successful claims against sheriffs statewide, Hopper said.

Jones, a cashier at a Giant Food store, was arrested in February 1986 after an altercation with an Alexandria police officer. She pleaded guilty April 18, 1986, to a misdemeanor of impeding an officer in Alexandria General District Court and was given a 3 1/2-hour sentence.

A sheriff's deputy put her in a holding cell that Friday morning, and forgot to release her before leaving for the weekend. Jones was discovered Monday morning when the building was reopened.

Her 8-by-11-foot room contained only a bench, a light, a water fountain and a toilet. During her 69-hour ordeal, Jones passed out several times and was forced to drink from the toilet because the fountain was not working, her attorney said.

As a result of the experience, Jones had to seek medical care for loss of appetite and psychological stress, Goldson said.

Sheriff's Deputy Vernell Bolton, who placed Jones in the cell, resigned a few days after the incident, which occurred a few months after Dunning assumed his post. He had run for election the previous year on a pledge to improve the management of the sheriff's office.

Dunning said yesterday that after Jones' experience, he ordered improved procedures for checking and supervising prisoners to prevent such an incident from recurring.

Jones also has filed suit against Alexandria police Officer Joseph A. Watson in Alexandria Circuit Court, alleging her arrest in February 1986 was unlawful and violated her civil rights. That suit is pending.

She was accompanied yesterday by her husband Garrett, 34, her stepdaughter, Tamika, 15, and daughters Ebony, 10, and Charmaine, 8 months.