A federal jury yesterday rejected a $20 million injury claim brought by a Fauquier County woman who was severely burned two years ago in a county jail cell after a lighted match ignited her mattress.

The verdict, returned after a four-day trial in U.S. District Court in Alexandria, followed graphic testimony by the burn victim, Vivian Hitt, who said she had begged to die during a painful four-month recovery at a Washington hospital.

"That's not me. You have to be lying to me," Hitt said she cried when a nurse at Washington Hospital Center first held a mirror to her face. Hitt, 22, suffered burns over most of her body because, she claimed, jailers were slow to respond to her screams for help.

Attorney Jack B. Stevens, representing defendants Luther Cox, sheriff of Fauquier County, and former jailer George West, argued that Hitt contributed to her injuries by her own alleged negligence in causing the Feb. 3, 1980, fire that engulfed her 5-by-7 foot cell.

Hitt was stopped by police about 3 a.m. and ordered jailed for four or five hours by a Warrenton magistrate because she was too intoxicated to drive, according to trial testimony. Hitt acknowledged the fire started shortly before dawn after she lit a cigarette and threw the match over her shoulder without noticing it had landed on the mattress.

Fauquier County, originally named as a defendant, was dropped from the suit after reaching a pretrial settlement with Hitt. Stevens said yesterday the county has agreed to pay Hitt $350,000 and that the settlement could reach $500,000 depending on discussions between the county and its insurance carrier.