Jury selection in the trial of a man charged with killing one of the few late-term abortion doctors in the U.S. was delayed Monday after prosecutors challenged a judge's decision to allow the defense to build a case for a lesser charge.

A hearing was set for Tuesday afternoon to give the defense an opportunity to respond to prosecutors' court filing. Jury selection was expected to begin Wednesday in Scott Roeder's trial.

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Roeder, 51, faces a premeditated, first-degree murder charge in the May 31 shooting of Dr. George Tiller, who was gunned down while serving as an usher at his Wichita church. Roeder also is charged with two counts of aggravated assault for allegedly pointing a gun at two ushers who tried to stop him after the shooting.

Roeder has admitted to reporters and in a court filing that he killed Tiller to save "unborn children."

The judge in the case allowed defense attorneys on Friday to try building a case for the lesser charge of voluntary manslaughter by presenting evidence that Roeder sincerely believed the slaying was necessary to save unborn babies.

Prosecutors argued in their filing that such a defense, known as an imperfect self-defense, is not appropriately considered with premeditated first-degree murder when there is no evidence of an imminent attack at the time of the killing.

"The State encourages this Court to not be the first to enable a defendant to justify premeditated murder because of an emotionally charged political belief," the prosecution wrote. "Such a ruling has far reaching consequences and would be contrary to Kansas law."

Abortion has been legal in the United States since a 1973 Supreme Court ruling, but it remains a controversial issue.

By the time Roeder shows up at the Sedgwick County courthouse for the start of his trial, the court would have summoned 300 prospective panelists. A first group of 61 had been expected Monday.

The lawyers will winnow the pool to 12 jurors and two alternates who will hear an expected two weeks of testimony.

Jury selection will likely consume much of the first week as lawyers sort out the impact of pretrial publicity and jurors' medical histories and attitudes over abortion and health care.