A jury decided yesterday that the owner of a chain of men's clothing stores must pay $150,000 to his ex-wife's attorney for striking the lawyer with a briefcase in an altercation in the Fairfax County Courthouse in May 1983.

The seven-member Fairfax Circuit Court jury deliberated 65 minutes before returning its verdict that John Dashtara, owner of Dash's Designer Clothes, must pay $50,000 in compensatory damages and $100,000 in punitive damages to David Moyes.

Moyes, a lawyer with a practice in Fairfax and Loudoun who is also a horseman with a farm in Waterford, Va., testified that Dashtara struck him in the groin with a briefcase during an exchange of words in a Fairfax County Courthouse hallway after a bitter child custody hearing.

Moyes told the jurors the pain from the incident was "extreme. I don't know that I can describe it. But it was very, very painful."

Moyes said his urine was bloody shortly after the incident, he was unable to walk during the two days following it and his vigorous, daily horse riding schedule has been severely curtailed.

Dashtara, who was previously convicted of misdemeanor assault and battery in the attack and fined $1,000, took the stand and denied striking Moyes.

His attorney, John E. Kilcarr, told the jury: "If there was a touching, it was not an intentional touching." Kilcarr also suggested to the jury in closing argument that the injury that sent Moyes to a urologist three times was caused by his horse riding.

A urologist testified that Moyes' injury, which will eventually heal, was not the sort of injury to be caused by riding.

Kilcarr said after the verdict that no decision had been made on whether to appeal.

The May 13, 1983, altercation occurred just outside Courtroom 5G, the same courtroom where yesterday's trial of Moyes' civil lawsuit took place. After a brief but acrimonious hearing, according to testimony, there was a confrontation between Moyes and Dashtara.

Yesterday Moyes left the witness stand and took the briefcase in hand to demonstrate for the jurors.

Swinging the briefcase back and then all the way through in front of him with his right hand, he said Dashtara "swung it back -- as he was talking to me and walking toward me -- and then he swung it up underneath my groin . . . . He did it with quite a bit of force. That's what I remember vividly."