Attorney General John D. Ashcroft yesterday proposed spending more than $1 billion on DNA analysis in criminal cases over the next five years, vowing to eliminate a massive backlog that has left hundreds of thousands of genetic samples untested nationwide.

The plan, first suggested in President Bush's 2004 budget proposal, envisions a dramatic expansion of an FBI database that contains DNA profiles from across the nation, a move that would improve chances of matching samples recovered at crime scenes. The government also would provide millions of dollars to state and local governments for DNA testing in criminal cases.

The proposal would significantly increase the federal government's involvement in DNA testing, which has been widely acclaimed as a reliable tool for convicting or clearing criminal suspects and has played a central role in the ongoing national debate over the death penalty.

But some legal advocates immediately criticized the plan, because it offers relatively little funding for DNA testing by criminal defendants seeking to prove their innocence, and a leading Democratic lawmaker complained that the proposal came after years of inaction by the Bush administration.

The National Institute of Justice, an arm of the Justice Department, estimates that as many as 350,000 DNA samples remain unexamined in homicide and rape cases nationwide. As many as 300,000 samples collected from convicted offenders also have not been tested, the agency found.

The Bush administration proposal, which aims to clear the testing backlog in five years, would nearly double annual federal funding for DNA analysis to $233 million. Some of the money would be used to train scientists, prosecutors and others.

Ashcroft, joined at a Washington news conference by "America's Most Wanted" host John Walsh and victim advocate Kellie Greene, billed DNA technology as a way to solve crimes and prevent more offenses from being committed.

"We can solve more crimes through DNA testing, and we can do it by eliminating the substantial backlog of DNA samples for the most serious violent offenses," Ashcroft said.

Greene, a Florida sexual assault victim whose attacker was identified through DNA testing, said that "to this day, the only reason I know what the rapist looks like is because DNA tells me."

The FBI's database contains about 1.3 million DNA samples and has yielded more than 6,000 matches in criminal investigations, including probes into the Sept. 11, 2001, terrorist attacks and the deadly anthrax mailings, officials have said.

Most of the proposed new funding would focus on identifying and prosecuting criminal suspects, with just $5 million a year allocated for post-conviction tests that can be used by defendants to prove their innocence.

Barry C. Scheck, a founder of the Innocence Project at the Benjamin N. Cardozo School of Law in New York, said the administration's proposal "is long overdue" but will not do enough to protect the rights of defendants. Scheck cited the release of a man in Houston this week who served four years in prison after being wrongly convicted of rape because of mistakes in processing DNA evidence.

The Innocence Project reports that 123 people have been exonerated through post-conviction DNA testing, including 12 death row inmates.

"It's good the administration is doing this in using DNA as an investigative tool, but you can't have a one-sided approach to criminal justice," Scheck said.

A senior Justice Department official said that $5 million a year should be more than enough to cover the cost of post-conviction DNA tests, which generally cost $4,000 to $5,000 each. This official said that the demand for such tests is very limited, because many defendants are reluctant to offer DNA samples voluntarily.

Sen. Patrick J. Leahy (D-Vt.), the ranking Democrat on the Senate Judiciary Committee, said the Bush administration proposal comes after "years of shortchanging the nation's crime labs." Leahy is a lead sponsor of legislation that would give death row inmates the right to request DNA testing.

The FBI plans to ask Congress to let the bureau collect all DNA samples from the states, including those from Virginia, Louisiana and Texas that are taken from people who have been arrested but not convicted of crimes.

The Justice Department also published proposed rules yesterday that would expand the list of federal crimes that would merit inclusion in the FBI's DNA database, including most crimes related to terrorism.

In a separate briefing yesterday, Ashcroft told reporters that the Justice Department will concentrate on three priorities in enforcing environmental laws and attempt to link those laws to homeland security.

Ashcroft said one priority is to use the enforcement of environmental protection and safety laws to enhance the security of facilities such as pipelines, storage tanks, transportation networks and water supplies. He said the other priorities are to prevent polluting companies from gaining an economic advantage over their law-abiding competitors, and to step up attempts to recover the cost of enforcing the Superfund program for the cleanup of toxic waste sites.

Staff writer Edward Walsh contributed to this report.

Attorney General John D. Ashcroft displays a chip that speeds up DNA analysis. With him is Kellie Greene, a sexual assault victim whose attacker was found by DNA testing.