With Maryland's first execution in six years barely a month away, attorneys for murderer Steven Oken yesterday filed the first in what they say will be a series of motions to attempt to save his life by challenging not just how he was convicted but how the state would put him to death.

The argument submitted yesterday to Baltimore County Circuit Court is essentially a narrow compliance issue centering on Maryland's procedure for lethal injection. But Oken's defense will expand its effort next week with a broader attack on the manner of execution, which it says is so cruel and unusual as to violate state and federal law.

That very claim was made a decade ago on the eve of the execution of John F. Thanos, the first person to be put to death in Maryland since the state reinstated capital punishment. A Baltimore judge rejected the appeal, and the state's highest court refused to intervene.

Since 2000, however, similar claims have been raised increasingly in cases across the country. Their impetus has been legislative moves in nearly two dozen states to prohibit one of the chemicals integral to lethal injection from being used in animal euthanasia. Death penalty opponents ask: If the paralytic agent pancuronium bromide is outlawed for putting cats and dogs to death because of the suffering it can cause, how can it be used on people?

"That's what has fueled the argument," said David R. Dow, a law professor at the University of Houston who has represented numerous inmates on Texas's death row. "Facts change, and the changing facts shape legal doctrine."

In the context of the Eighth Amendment and what the Supreme Court has described as its "evolving standards of decency" on capital punishment, those changing facts suddenly can render unconstitutional what previously was allowed.

That line has yet to be crossed on this issue; of the more than half-dozen appeals contesting lethal injection to reach the Supreme Court this year, Dow said that not one was successful in staying an execution. In every case, the vote was 5 to 4.

Oken, 42, has twice before faced a countdown to his death for the 1987 sexual assault and murder of Dawn Garvin, a college student and newlywed killed in her Baltimore County apartment. Hours after his latest warrant was signed April 27 -- setting the week of June 14 for his execution -- his longtime attorney, Fred Bennett of Greenbelt, vowed to pursue every legal channel to save him.

"We had expected that there would be some challenge to the method of execution," Maryland's solicitor general, Gary Bair, responded yesterday.

Bennett's first salvo is "one of about five or six issues" that the defense attorney said he plans to raise. The motion contends that the Division of Correction does not follow Maryland law because officials administer a trio of drugs during a lethal injection while the statutory language specifies just two: "an ultrashort-acting barbiturate or other similar drug combination with a chemical paralytic agent," given intravenously until death is pronounced.

In the three executions carried out in the past decade, Maryland used sodium pentothal to render the condemned inmate unconscious and Pavulon, the brand name for pancuronium bromide, to stop his breathing by paralyzing his diaphragm and lungs. But its final action was a large dose of potassium chloride to interrupt the body's electrical network and cause cardiac arrest.

According to the state Division of Correction, the procedure lasts about seven minutes, "the worst physical pain being the prick of a needle."

Bennett disagrees vehemently. "The court should declare the Execution Procedures invalid and void" and should vacate the execution warrant in favor of an emergency hearing, he wrote in his filing.

The defense attorney said yesterday that he also will move to reopen the case based on recent Supreme Court decisions that could allow Oken to raise new legal issues regarding his conviction and sentencing on both constitutional and evidentiary grounds.

The bar for doing so is exceedingly high, Bair noted. "He is looking for something," he said. "That doesn't mean it's something that will ever be heard."