A judge is weighing a critical legal question in the case of a man who confessed to killing one of the nation's few late-term abortion providers: Can the man claim at his trial that the slaying was justified to save the lives of unborn children?

Scott Roeder, a 51-year-old Kansas City, Mo., man, is charged with one count of premeditated, first-degree murder in Dr. George Tiller's death and two counts of aggravated assault for allegedly threatening two ushers during the May 31 melee in the foyer of the doctor's Wichita church.

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District Judge Warren Wilbert has yet to rule on a bevy of court filings that will set the course for the Jan. 11 trial, and will consider some of them in court Tuesday. But the documents offer a glimpse at the unfolding legal strategies in a case played out amid the rancorous debate over abortion.

Since the killing, Roeder has confessed to reporters that he shot Tiller, while his anti-abortion allies have urged Roeder to present the so-called "necessity defense" in hopes that an acquittal could turn the larger debate over abortion in their favor.

"I choose this action I am accused of because of the necessity defense," Roeder told The Associated Press in November. "I want to make sure that the focus is, of course, obviously on the preborn children and the necessity to defend them."

If the judge rejects that defense, Roeder and his attorneys would not be allowed to make that argument to jurors at his trial. Similar efforts to use such a strategy in cases involving abortion-related violence have generally been banned — perhaps most relevantly at the 1993 trial of an Oregon woman accused of shooting and wounding Tiller.

Roeder, who has pleaded not guilty, confessed to the shooting on Nov. 9, telling The Associated Press he has no regrets for killing Tiller and suggesting the necessity defense should be the only contested issue of his trial. Roeder declined to say when asked if he would kill another abortion provider if he were acquitted.

The so-called "necessity defense" has rarely been successfully used in abortion cases. Roeder's attorneys — while arguing that their client has a right to present his theory of defense — have so far kept their own strategy secret.

Legal experts and others close to the case have suggested his public defenders may actually be aiming at a conviction on a lesser offense such as voluntary manslaughter — defined in Kansas as "an unreasonable but honest belief that circumstances existed that justified deadly force."

That would be an easier argument to make to jurors than a necessity defense, which is unlikely to win, said Melanie Wilson, a University of Kansas law professor. A necessity defense, also known as the "choice of evils defense," requires proof that the defendant reacted to an immediate danger, an argument that is undermined by abortion's legality.

"The defendant has a right to a defense and so if he can put forth evidence that shows adequate facts to support such a defense, well then he should be allowed to do so," Wilson said. "I suspect that is what the big fight is going to be at the motions hearing."

A wild card is Roeder's close relationship with Iowa anti-abortion activist Dave Leach, who has been separately crafting a necessity defense for Roeder — including writing motions that could be used if Roeder were to represent himself. Leach said the goal is to encourage states to criminalize abortion again or at least bolster a defense that would allow activists to block clinic entrances without fear of arrest.

"My strong conviction is that this case presents an opportunity, through education of both the public and the courts, to end abortion," Leach said.

Prosecutors want to block such notions, citing a criminal trespass case involving an abortion clinic in which the Kansas Supreme Court ruled that allowing someone's personal beliefs to justify criminal activity would be "tantamount to sanctioning anarchy."

Roeder's two public defenders responded that Roeder's case differs because trespassing at an abortion clinic is just a potential temporary interruption of the practice of abortion, whereas Roeder succeeded in shutting down Tiller's clinic.

If convicted of first-degree murder, Roeder faces a life sentence with the possibility of parole after 25 years. A conviction for voluntary manslaughter for someone with as little criminal history as Roeder could bring a sentence closer to five years if the judge follows state sentencing guidelines.

Roeder's public confession notwithstanding, prosecutors have overwhelming evidence against him — chiefly the eyewitnesses who identified Roeder as the shooter during a preliminary hearing in July. Legal experts say the prosecution will likely want to keep the case limited to a straightforward murder case and avoid a discussion of abortion.

"The defense would rather have it be a trial of abortion — particularly late-term abortion — and not a trial of the killing of Dr. Tiller," said Richard Levy, a law professor at the University of Kansas. "It is often a sound defense strategy to go after the victim."