Virginia Gov. Mark R. Warner on Thursday ordered DNA testing in dozens of old criminal cases to determine whether modern-day examination of biological samples will exonerate people convicted of violent crimes and still held in Virginia prisons.

Warner (D) said the state should not wait until inmates request DNA testing under state evidence laws that were relaxed by the legislature three years ago. Instead, Warner said the state will spend about $200,000 to evaluate and test about 40 cases after culling through about 10 percent of those on file in state archives from the 1970s and 1980s. A majority will be sexual assault cases.

In a letter released Thursday afternoon, Warner's chief counsel instructed the head of the state's DNA laboratory to initiate testing at an independent lab.

"The governor has directed the Division of Forensic Sciences to carry out an evaluation of old serology cases using new DNA technologies," wrote Robert M. Blue, the governor's top lawyer. "Once this testing is completed, the governor will review the results . . . to determine whether any further review and testing . . . would be productive."

The governor's order came as the Virginia Trial Lawyers Association urged the state to go further by testing all of the old cases in which biological samples still exist. In a letter sent to Warner, it urged him to move more quickly to test biological samples in criminal cases.

"Such materials may prove to be a treasure trove for those wrongly imprisoned and a final reckoning for the guilty," wrote H. Duncan Garnett Jr., the group's president. "How many more innocent people will have to be disgorged from Virginia's prisons before our state lab finally acknowledges that decisive steps are needed?"

Still, some defense attorneys hailed Warner's move as a significant step toward identifying those who have been wrongly imprisoned.

"There's a huge sea change in the attitude of getting to the truth in these cases through DNA testing," said Peter Neufeld of the Innocence Project at the Benjamin N. Cardozo School of Law. "Once you do these audits, you'll start finding more and more innocent people, and then you can start running the evidence through DNA databases and get the real criminals."

Del. Brian J. Moran (D-Alexandria), a member of the Courts of Justice committee, said: "DNA is a valuable tool to determine guilt or innocence. Hopefully, these tests will validate these convictions. But if the person's innocent, why do we want to establish some barrier to that determination?"

Warner's directive is the latest shift in a radically altered legal landscape in Virginia, which until recently had blocked inmates from seeking DNA testing unless they did so within three weeks of their first conviction.

That "21-day rule" was eased for DNA evidence three years ago, allowing inmates to seek newly available testing of biological information -- hair samples, semen or other bodily fluids -- long after they were convicted. And this year, lawmakers relaxed it further, allowing some inmates to request new trials on the basis of evidence other than DNA.

But until Warner's action Thursday, it was left to inmates to initiate the legal review process.

A few have. In recent years, DNA testing has exonerated three high-profile inmates who had each served years behind bars for crimes they did not commit.

In May 2003, Warner pardoned Julius Earl Ruffin, 49, of Virginia Beach, who spent 21 years in prison for a rape he did not commit. Marvin Lamont Anderson of Hanover County was cleared by DNA evidence in 2001 after serving 15 years in prison for rape.

Warner's decision to conduct the random tests was sparked by those cases and last month's exoneration of Arthur Lee Whitfield, a Norfolk man who spent 23 years in prison for two rapes he did not commit. The three are among more than 100 inmates across the country who have been freed by DNA evidence in recent years.

Gordon Zedd, an attorney who represented Ruffin, applauded the move to examine old cases. But he said it is not enough to pick only a few from thousands of files, despite the expense.

"These people, who have been jailed for this amount of time, are the most helpless people of all," Zedd said. "Wouldn't it be worth it if you find just one innocent person?"

Opponents of relaxing the 21-day rule have argued that the state should not reopen cases that were settled and given numerous opportunity for appeal. They have said that requesting testing should be left up to the inmates and their attorneys.

Attorney General Jerry W. Kilgore (R) supported easing the 21-day rule to allow DNA testing. His spokesman, Tim Murtaugh, said the attorney general had not seen the details of Warner's Thursday order.

But recently, he said Kilgore questioned the need for widespread testing.

"He has observed that we already have a process by which an inmate can request testing," Murtaugh said.

Staff writer Chris L. Jenkins contributed to this report.

Gov. Mark R. Warner said about $200,000 will be spent for the testing.