A judiciary battle is unfolding in Northern Virginia where circuit courts in Fairfax and rapidly growing Loudoun and Prince William counties are vying for additional state judgeships.

Fairfax judges and the local bar association have requested two more $54,000-a-year judges. Loudoun court officials have requested one. Prince William officials have made no formal request for a new judge, but are studying their increasing case load with an eye to another judgeship after receiving an additional one just last year, said Fred Hodnett, assistant executive secretary to the Virginia Supreme Court.

The 15-member state judicial council will meet Oct. 20 to make its recommendations on the requests that will then be acted on by the state legislature.

But Fairfax may well be the loser in this competition, because it has more judges than the other two counties put together and slower population growth.

"It may be that the state legislature will recommend that they Fairfax get one judge now and one later," Hodnett said. He said it was rare for any court to get more than one new judgeship in a year.

The competition for judges pits the two growing but largely rural counties against Fairfax, where a prosperous and sophisticated citizenry and increasing crime rate have flooded the courts with trials, making the county the busiest of the three courts in 1980, the last year statewide figures are available:

That year, the nine Fairfax judges handled an average of 1,368 cases each, making their load the eighth highest among the 31 state circuit courts.

The three Prince William judges handled an average of 1,126 cases each, ranking them ninth.

Loudoun's two judges, who also serve Fauquier and Rappahanock counties, had an average case load of 1,059 last year, ranking them 24th in Virginia.

"The judge is in here at 7:30 every morning and stays late almost every night just to keep his head above water," said Loudoun County clerk Frederick Howard.

"It's very lonely in the county when you are up here all by yourself," said a judge in one of the two rural counties vying with Fairfax. "Not only does Fairfax have a staff, they have law clerks to do research. I don't have a court administrator or law clerks. Sometimes I spend 45 minutes on the road just to travel between courthouses."

But Chief Fairfax Circuit Court Judge Barnard F. Jennings said Fairfax "has a tremendous backlog of cases. Certainly we can make a good case for our request . . . It would take about a year to clear out our backlog if no new cases were filed."

William F. Parkerson, chairman of the state Senate Courts of Justice Committee, said population growth may well be more important than case load in deciding where to add judges.

The state judicial council in the past has recommended that each jurisdiction have at least one judge for every 50,000 people, he said. That could thwart Fairfax's bid for additional judges, since during the last 10 years the population in Loudoun and Prince William has grown at a rate double that of Fairfax.