Scott Roeder's lawyer said Wednesday that the law prohibits holding his client without bail in the killing of Wichita abortion provider George Tiller.
Steve Osburn, head of the regional public defender's office, has filed a motion citing a state law that says courts must set bond for defendants charged with non-capital crimes.
Roeder was ordered held without bond Tuesday after his first court appearance.
The Kansas Constitution and an 89-year-old opinion from the Kansas Supreme Court appear to prevent holding defendants without bail except in cases that could bring the death penalty.
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Roeder is charged with first-degree murder, a non-capital offense, in Sunday's shooting of Tiller in the foyer of Reformation Lutheran Church in Wichita.
Osburn's motion could be heard as early as Friday, although no hearing has yet been scheduled.
Sedgwick County District Judge Ben Burgess, who assigns criminal cases, said Wednesday afternoon that he would likely assign the hearing to Judge Warren Wilbert.
Burgess said that he ordered no bail for Roeder as "a discretionary decision taking public safety into account."
Since 1920, the Kansas Supreme Court has held that judges couldn't withhold bail except in capital cases with the strongest evidence.
"In all other cases, the admission to bail is a right which the accused can claim, and which no judge or court can properly refuse," the justices wrote.
Section 9 of the Kansas Bill of Rights in the state constitution says: "All persons shall be bailable by sufficient sureties except for capital offenses."
Roeder, 51, was given a public defender after filling out a court affidavit saying he couldn't afford to hire an attorney. He listed his occupation as working for an airport delivery service making $1,100 a month. He listed previous employers as a convenience store and a party supply store.
Judges in Sedgwick County have routinely granted bonds in capital murder cases over the past decade. But bail has been set so high, the defendants couldn't afford to post it.
Reginald and Jonathan Carr, charged with killing five people during a 2000 crime spree that included robbery, rape and sodomy. The Carrs were held in lieu of $10 million bond.
Cornelius Oliver, charged with killing four people in 2000. Oliver's bond was set at $1 million.
Douglas Belt, charged with raping and decapitating a woman in 2002. He was ordered held under a $2.5 million bond.
Ted Burnett, charged with strangling a 14-year-old pregnant girl in 2006. Burnett was held under a $1 million bond.