An attorney for Washington Redskins running back John Riggins, who was arrested in July on a misdemeanor charge of being drunk in public, has filed a pre-trial motion in Fairfax County General District Court contending the arrest was invalid.

Defense attorney Jerry M. Phillips said yesterday he filed the motion to suppress the evidence in the case because "there was a lack of probable cause for him to be arrested." Phillips said his motion will be heard in court Tuesday, two days before the scheduled start of the trial.

"He's contesting this because he's not guilty," said Phillips, adding that he could not talk about the facts of the case. Riggins could not be reached for comment. It is expected that Riggins, the county police officer who arrested him and another witness will be called to testify at the hearing.

Riggins, 36, was getting a ride home from longtime friend Stuart Miller, 40, about 1:50 a.m. on July 25 when Miller's car was pulled over by a Fairfax County police officer in Reston. Miller was charged with driving while intoxicated, also a misdemeanor, and Riggins was charged with being drunk in public.

Miller, co-owner of Dixie Liquors in Georgetown, was found not guilty of DWI last month by Judge Steward P. Davis after Miller claimed his cowboy boots made him lose his balance during a sobriety test.

"The reason that Stuart Miller was acquitted was because he was not drunk, as shown by the breath test of 0.09," Phillips said yesterday. "Based on the testimony given at the trial of Stuart Miller and what the officer has already disclosed as his reason for charging John Riggins, we believe there are insufficient legal grounds for him being charged."

Police spokesman Warren R. Carmichael has said that Riggins, who was not given any field tests, offered no resistance and cooperated fully with the officer, but that Riggins "appeared obviously intoxicated to the officer."

Miller said outside the courthouse after his trial that Riggins was not drunk in public. "He was basically very mild mannered," he said. "I don't know what was going through the officer's mind."

If the motion is rejected, Phillips said yesterday, he will ask that the trial be postponed because of a conflict in his schedule.