Nearly a dozen current and former Fairfax County employes testified in U.S. court in Alexandria yesterday that the county discriminates against blacks and women in both its hiring and promotion policies.

"We feel that Fairfax County's performance in employing blacks has been low and slow, "Audrey Williams, a member of county's Human Rights Commission. "We certainly feel that much more can be done."

"The attitude of commitment [to equal opportunity] doesn't seem to be there unless they are forced," said Lee T. Young Jr., a former county worker and black community activist from Herndon.

The testimony came on the first day of a trial before U.S. District Court Judge Albert V. Bryan Jr. in a discrimination suit brought by the U.S. Justice Department against the county last November. The Justice Department which rested its case yesterday, charges that county officials have failed to meet the standards of the county's own affirmative action plan.

Assistant County Attorney Jack Gould will begin presenting the defense case today, when he is expected to call several top county officals as witnesses.

Among the federal government's evidence introduced yesterday was an array of statistics and maps intended to back the government's argument that the county has failed to seek qualified black and female applicants for jobs.

The federal government's witnesses included Chris Stokes, who in 1967 became Fairfax County's first black police officer. Stokes said that when he applied for the job, he had to take a polygraph test that lasted tw hours and 20 minutes.

Six whites who applied with him also took the test, he said, but theirs lasted only 50 minutes. Stokes, who was a highly decorated detective in the Richmond Police Department, also was the county's first community relations officer, he said.

Stokes testified that another officer assigned to the community relations office told Stokes that the other officer's job was to keep an eye on Stokes. Stokes, who lef the police force in 1973, said his repeated attempts to become a detective in Fairfax failed, apparently because he was black.

The witnesses also included a number of women who challenged the fairness of county promotion policies "I have gotten the feeling that the clerical positions are for women . . . the technical positions are to be filed by men." said Carla Turner, a clerk in the Department of Enviromental Management. She said her own attempts to win promotion failed.