Two Northern Virginia police officers and a polygraph examiner testified yesterday that Marine Cpl. Lindsey Scott's chief alibi witness has lied under oath in the past and is generally untruthful.

The alibi witness, former Zayre store detective Cynthia K. Ausby, later denied the allegations to reporters outside the courtroom, suggesting they were prompted by bruised egos and a thirst for publicity. "This case is turning people into demons," she said.

The testimony yesterday came from the prosecution's rebuttal witnesses after Scott's defense rested its case. The defense is expected to respond with rebuttal witnesses of its own today, after which closing arguments by both sides are scheduled. The case could go to the jury of seven Marine officers this afternoon.

Ausby testified at Scott's court-martial last week that she saw Scott shopping 12 miles from Quantico Marine Corps base around 8:15 p.m. on April 20, 1983.

That is the same time and date that the wife of a military policeman said she was abducted, raped, sodomized and slashed by a man she has identified as Scott.

Scott has denied the charges, insisting that he was shopping for a birthday present for his wife at the time the woman was attacked.

Ausby's testimony is a critical tenet of Scott's defense, for she is the only witness who has corroborated Scott's account of his activities on the night of the crime. Marine prosecutors have assailed her credibility ever since she changed her story after Scott's first court-martial in 1983, when she said under oath that she could not remember what date she had seen Scott.

Scott was convicted in the 1983 trial and sentenced to 30 years at hard labor. The conviction was set aside last summer and the Marine Corps decided in October to convene a second court-martial.

One of the witnesses yesterday, Fairfax County police Officer Terry Lee Maxwell, was Ausby's supervisor when she worked at Zayre in Woodbridge. As a Zayre detective, Ausby appeared in court frequently to testify against shoplifting suspects. Maxwell, who described herself as Ausby's friend, said Ausby had once testified in court that she had seen two women fill their purses with items from the shelves at Zayre.

In fact, Maxwell said, Ausby had stated earlier that she had not seen the women shoplift, but apprehended them based on the appearance of their purses. Asked if she would believe Ausby's testimony under oath, Maxwell replied, "No."

Ausby, now a licensed private investigator, told reporters that she didn't know what had prompted Maxwell's testimony, but speculated that witnesses may be coming forward because of reports of a planned television "docudrama" on the case.

Two other prosecution witnesses, Prince William County police Capt. Charles E. O'Shields and polygraph examiner Allan R. Marlett, testified that Ausby had lied to them in interviews when she applied to become a police officer in 1981. Both said they would not believe her testimony.

Neither man mentioned or was asked for particulars -- the military rules of evidence exclude the introduction of such testimony on direct examination. Nor was there any testimony that Ausby lied in a polygraph exam. Ausby has said -- and prosecutors confirm -- that she passed a polygraph exam administered by Prince William police.

Sources said, however, that both men were referring to Ausby's statement that she had once lied under oath, telling a court that she had nabbed a shoplifter after the suspect left the store, when in fact the arrest occurred inside. Generally, it is difficult to convict shoplifters unless they leave the store premises with stolen goods.

Ausby denied it, declaring, "I never nabbed anyone inside in my life." She said O'Shields was testifying against her because she had "stepped on his toes" by filing a sex and race discrimination complaint against him after she was denied a job with the Prince William police.

Earlier in the day, the military judge, Lt. Col. Eligah D. Clark, denied a motion by defense attorneys to delay the case by at least eight weeks pending the results of further tests on DNA in semen recovered from the victim's underwear. Tests last week were inconclusive.