An Arlington jury yesterday sentenced Timothy W. Spencer to death for the rape and strangulation of an Arlington woman in Virginia's first criminal case involving genetic evidence.

"It's an appropriate verdict. Spencer is a very dangerous individual," said Commonwealth's Attorney Helen M. Fahey, who said the case was the first in the country in which genetic evidence led to a death penalty sentence.

"It's important that the evidence was admitted by the court, and just as important that it was accepted by a jury in a capital case," she said.

Spencer displayed no emotion when the death sentence was read.

The eight-woman, four-man jury took a little over an hour to reach its decision after a full day of testimony in the six-day trial's penalty phase.

Several jurors contacted after yesterday's session declined to discuss the case.

Circuit Court Judge Benjamin N.A. Kendrick will impose the sentence Nov. 4. Kendrick could reduce the penalty to life in prison.

All death penalty sentences are automatically appealed to the Virginia Supreme Court.

Thirty-four persons are on the state's death row in Mecklenburg.

Spencer's attorney, Carl J. Womack Jr., said last night that the defense had not decided whether to challenge the validity of the genetic tests on appeal.

Genetic tests analyze the DNA (deoxyribonucleic acid) found in hair, semen, blood and other bodily fluids.

The substance determines an individual's genetic makeup, and, with the exception of twins, no two people have the same genetic code.

Spencer, 26, was convicted Friday of raping and murdering Susan M. Tucker, 44, who was found Dec. 1 in her Fairlington town house.

Spencer, who lived in Richmond, was in Arlington visiting relatives over the Thanksgiving weekend, when Tucker is thought to have died.

There were no witnesses placing him at the scene of the crime; instead, the key evidence was the results of the genetic testing.

The DNA from semen found on Tucker's nightgown and a sleeping bag was identical to DNA extracted from a sample of Spencer's blood. An expert testified during the trial that the odds are at least 135 million to 1 against an unrelated male having DNA identical to Spencer's.

During the penalty phase of the trial, prosecutors argued that Spencer is a serial rapist and murderer and presents a continuing danger to society.

The state yesterday presented testimony and evidence, including the results of DNA tests, linking Spencer to the rape and slaying last fall of two Richmond women.

Fahey pointed out similarities between their slayings and Tucker's: All three women were strangled and found with their hands tied behind them. Two of the women, including Tucker, were married but their husbands were out of town when the slayings occurred.

"Something is terribly, terribly wrong with Timothy Spencer," Fahey said.

Spencer has been charged with capital murder in the Richmond killings but has not yet been tried. Virginia law allows introduction of un-tried acts as an indication of an individual's likelihood of committing future crimes, prosecutors said.

The DNA taken from both Richmond crime scenes matched DNA found in a blood specimen from Spencer "in every respect," said Lorah McNally, a forensic scientist employed by Lifecodes, a New York firm that performed the testing.

Spencer, taking the stand on his own behalf, denied killing any of the women. "I feel sorry for their families. I didn't kill those ladies," he said. "Sentence me to anything besides sentencing me to death."

Seven witnesses testified on Spencer's behalf, describing him as a loner as a child and as "friendly, quiet {and} always with a smile on his face" as a state prisoner. Spencer has three juvenile and three adult convictions for burglary, and has been in jail a great part of his adult life.

Spencer's mother, Thelma Spencer, was one of those who testified on his behalf. "It's been hard on him, and I'm sorry that it happened from the bottom of my heart."

In closing arguments, Womack said Spencer's resentment of his mother was the motivation for the crime. "Every time, he's killing his mother," Womack said.