Prince William County Circuit Court Judge Percy Thornton Jr. yesterday turned down a request that anupcoming felony gambling trial of Alexandria prosecutor William L. Cowhig be tried without a jury.

Thornton, in a pretrial hearing in his Manassas courtroom, also denied a related motion by Special Prosecutor Edward J. White to have jurors selected from outside of Alexandria.

White has failed twice to convict Cowhig, 53, of bingo-related felony bribery and gambling charges in two earlier trials in Alexandria Circuit Court. Jurors in those trials said later that they did not find testimony by some key prosecution witnesses believable.

Thornton also said yesterday he was considering reducing the remaining gambling charge against Cowhig to a misdemeanor because of ambiguities in Virginia's statute governing bingo. After a strenuous argument by White against such a move. Thornton agreed to let the felony trial begin as scheduled on March 5.

White argued yesterday that Alexandria had become "saturated" by publicity from the earlier Cowhig trials and asked that outside jurors be brought in as a matter of "fairness" and "practicality."

Defense attorney James C. Clark said his client would not waive his right to a jury trial, which automatically meant White's motion was denied.

Cowhig declined to comment after the hearing. He was accompanied by his longtime administrative assistant Mary Ann (Sam) Pastorek who was placed on a 30-day leave by Acting Commonwealth Attorney John E. Kloch earlier this week after Kloch and four members of his staff vowed to resign if Cowhig returned to office.

In reviewing the gambling charge against Cowhig, Thorton yesterday said that although the previous charge involved a bingo game for an organization "which did not even have the color of a nonprofit organization", the second bingo game was conducted in the name of Boy Scout post, which could have been legal under some circumstances. Bingo games, under Virginia law, must be conducted by charitable organizations.

But White argued that the scouting post "was basically a ruse to operate bingo" and cited recent judicial rulings in Alexandria and Fairfax County in which individuals who hid behind the names of charitable organizations "with or without their permission" could be prosecuted for illegal gambling.