A federal court jury found yesterday that two Fairfax County police officers used excessive force in arresting a motorist accused of speeding and awarded the plaintiff $4,500.

The civil suit, brought by Jonathan Walker of 2202 Cocquina Dr., Reston, apparently was the first such case Fairfax County has ever lost in defending county police against brutality charges, according the county attorney David T. Stitt.

According to Walker, he was returning home from his shift as a machine operator at the U.S. Postal Service mail sorting center in Merrifield when he was halted near his house by Fairfax officers Francis T. Noon III and Christopher A. Rizzo.

Walker claimed he was pulled from his car, dragged by his hair, handcuffed from behind and then pushed head first into the fender of his car.

Walker was charged with speeding and failing to stop after receiving a police signal. He told the jury he didn't hear the signal because his windows were rolled up and his stereo was turned on.

After the incident, which occurred May 16, 1979, Walker was found guilty of speeding but not guilty of the charge of failing to stop, according to his attorney, Sheldon I. Cohen. On appeal to Fairfax Circuit Court, Cohen said, Walker's speeding charge was reduced to improper driving.