When ``Freeway Killer'' William Bonin was executed by lethal injection 10 years ago, it seemed that arguments about what is a humane way to put inmates to death in California were finally over.

That assumption was wrong.

From California to Maryland, lawyers for death row inmates have mounted challenges to the use of lethal injection in virtually every state with capital punishment. And this week, California takes center stage in a widening legal battle over lethal injection that may be destined for the U.S. Supreme Court.

Starting Tuesday, U.S. District Judge Jeremy Fogel will hold an unprecedented four-day hearing in San Jose to explore whether the method the state uses to execute inmates violates the constitutional ban on cruel and unusual punishment. Fogel has effectively put a temporary halt to executions in California as he considers the legal challenge from death row inmate Michael Morales, who in February was hours from receiving a fatal dose of drugs when he was given a reprieve.

Other states have held hearings to examine lethal injection issues, but the California case is expected to be the most thorough inquiry to ever unfold in a courtroom. Fogel already broke new ground this spring when he toured San Quentin's death chamber to get a first-hand look at the mechanics of an execution.

``I think the Morales case and these hearings will be the most critical events of all the events that have happened in this area over the past year,'' said Deborah Denno, a Fordham University professor and leading expert on lethal injection.

Historic turn

In addition, the hearings, which will range from nitty-gritty testimony from medical experts to accounts from prison execution team members, mark a historic turn in California's effort to find an acceptable way to carry out death sentences in a state that now has 658 death row inmates, more than any other state.

Bonin was executed by lethal injection soon after California prison officials emerged from a costly and losing legal battle over San Quentin's gas chamber, which a federal appeals court had declared cruel and unusual punishment. To counteract the legal problems, California followed the lead of other states, such as Oklahoma and Texas, and enacted legislation that made lethal injection the preferred way of executing a condemned killer. Bonin was the first inmate in California to be executed that way.

``It made a whole lot of sense to me,'' said former San Quentin warden Daniel Vasquez, who led the effort to switch to lethal injection. ``Execution of a human being is not an easy thing to do, period. But in terms of viewing an execution by lethal gas and lethal injection, there is no question lethal injection is a lot more humane method.''

Today, 37 of the 38 states with the death penalty use lethal injection. The result has been a series of legal challenges that rely on the same central argument: that the combination of three drugs used to kill an inmate could mask a searingly painful death, creating a risk of cruel and unusual punishment.

In some states, judges have put executions on hold in response to such lawsuits. Earlier this month, a federal judge in Missouri halted executions until that state revises its method. South Dakota has halted executions until state officials change the lethal injection practices. In other states, executions have gone forward, including one last week in Florida.

Appeals certain

Whatever Fogel decides, he is unlikely to have the last word in the case because his ruling is expected to be appealed to the 9th U.S. Circuit Court of Appeals. Legal experts say the U.S. Supreme Court, which has never outlawed a method of execution, will eventually have to weigh in. But Fogel's review will offer those courts an unprecedented glimpse into the medical and legal questions surrounding lethal injection.

Fogel has not indicated how he may rule, but said recently in court he had no ``desire to micromanage'' the state's executions when he decides the outcome.

Under California's ``Protocol 770,'' the state's lethal injection procedure, prison officials administer three drugs to an inmate. The first, sodium thiopental, is the sedative that renders an inmate unconscious; the second, pancurium bromide, paralyzes the muscles in breathing; and the third, potassium chloride, stops the heart.

The crux of Morales' legal challenge is that the prisoner may remain semiconscious after the first drug is administered and the second paralytic drug then conceals an inmate's suffering when the third -- and, some argue, painful -- dose is administered.

The argument galls death penalty supporters and victims' family members. The family of Terri Winchell, a 17-year-old Lodi girl raped and murdered by Morales in 1981, has expressed outrage that he managed to avoid execution by challenging lethal injection.

In an e-mail, Barbara Christian, the girl's mother, said the case ``is just a ploy to stall execution.'' Winchell's brother also is angry.

``He should feel some pain,'' said David Winchell, who was at San Quentin in February when Fogel postponed the execution. ``Look at the pain he inflicted on my sister. The law is the law, and justice is justice, and justice is not being served.''

State prison officials have tinkered with the execution procedure in recent months. Among other things, the state would now administer a continuous dose of the sedative to ensure the inmate remains unconscious throughout the execution.

No quick fix

But Morales' lawyers, relying in part on newly revealed evidence of problems in past executions, say California does not have the safeguards to minimize the risk of a foul-up in an execution. And they say the state is violating the law by enacting execution procedures without public input.

``There are no quick fixes to this problem,'' said John Grele, one of Morales' lawyers.

In court papers, Morales' lawyers cite evidence that San Quentin fails to properly train execution team members, and pointed to major problems in the execution last year of former Crips co-founder Stanley ``Tookie'' Williams. A nurse was unable to set one of the catheters in Williams and ``blew a vein'' twice, according to court documents.

``The nurse was frustrated and upset,'' the documents stated, adding that she then left the chamber.

Senior Assistant Attorney General Dane Gillette acknowledged problems with the Williams execution, but insisted it was an isolated event that would not be repeated. Gillette argues that Morales has presented no evidence that there are systemic problems with lethal injection procedures, or that the drug doses cause an inmate to suffer.

``We're comfortable that the procedures California has are constitutionally sufficient,'' Gillette said. ``I see this case as a way to put this issue to rest once and for all in California. That's our objective.''

Contact Howard Mintz at hmintz@mercurynews.com or (408) 286-0236.