A jury convicted Lisa Rubin, 34, of first-degree murder last night for shooting her estranged husband to death on a wooded path near a Poolesville veterinary clinic where they had arranged to meet to have their sick dog destroyed.

Rubin testified Thursday that she shot Timothy Warner nine times in self-defense on April 24, reloading her .38-caliber Lady Smith revolver once, after he drew a pistol and threatened to kill her. She showed no emotion when the Montgomery County Circuit Court jury returned its verdict after deliberating five hours.

She could receive up to life in prison on the murder conviction and 20 years for using a handgun in the commission of a violent crime. Judge William C. Miller revoked Rubin's $100,000 bond and scheduled sentencing for Jan. 31.

Warner, 28, was an engineer for the National Aeronautics and Space Administration.

Several of his relatives and friends hugged each other and cried after the verdict. "I feel very, very saddened for Tim and Lisa," said Jack Warner, the dead man's father. "They were both my family. Justice has been done."

Rubin's attorneys, Alan Goldstein, Barry Helfand and Fred Joseph, said they plan to appeal on grounds that the trial breached attorney-client confidentiality rules.

"When in the history of Maryland has someone been convicted based on the testimony of a lawyer's private investigator?" Joseph said. "It happened in this courthouse tonight."

After the shooting, Rubin called Robert Miller, a private detective she had hired to conduct surveillance of her husband. Miller then took pictures of the slaying scene and helped have Rubin admitted to a hospital under a false name for an alleged drug overdose, according to testimony. The investigator worked for a firm that had worked for a lawyer who was representing Rubin at the time. Judge Miller ruled that the attorney-client confidentiality rule did not cover the situation.

In her testimony, Rubin, who lives in Bethesda, said she shot Warner after he "flew into a rage" when she told him she had asked police to investigate him as a suspect in an alleged attempt to poison a Secret Service agent who had been her lover. "I started firing. I just kept firing. He kept coming at me," she said.

According to testimony, Rubin bought a .22-caliber Beretta pistol and the Lady Smith handgun two weeks before the shooting. The manager of a Silver Spring gun shop testified that Rubin told him she wanted the guns for protection and for target practice with a girlfriend.

The Beretta registered to Rubin was found under Warner's body and had not been fired, police said.

In closing arguments, Mark Foley, the prosecutor who tried the case, portrayed Rubin as a domineering woman who plotted her husband's slaying after their marriage fell apart.

"This was a woman who was losing control of Tim Warner," Foley said. "That loss of control bothered her. She couldn't let it happen."

Foley said Rubin ambushed Warner near the Peachtree Veterinary Clinic and "shot him until he was dead."

Defense attorneys Joseph and Helfand urged the jury to believe their client. "This is not a made-up story," Joseph said.