(CNN) -- A man on trial for gunning down a Kansas abortion provider in church said he had no regrets because "abortion is murder."
Scott Roeder, 51, said he shot and killed Dr. George Tiller as services began on May 31 to save the lives of the unborn.
"There was nothing being done and the legal process had been exhausted, and these babies were dying every day," Roeder said. "I did what I thought was needed to be done to protect the children."
Roeder is charged with one count of first-degree murder for the death of Tiller, who ran a women's clinic in Wichita where abortions were performed, including the controversial late-term procedure.
Roeder was the only witness for the defense, which rested its case Thursday. Sedgwick County District Judge Warren Wilbert told jurors closing arguments will be held Friday morning, depending on the weather.
After the jury left, Wilbert ruled that the jury could not consider convicting Roeder of the lesser charge of voluntary manslaughter, which is defined as "an unreasonable but honest belief that circumstances existed that justified deadly force" under Kansas statute.
Wilbert said testimony did not support the defense claim that Roeder's beliefs on abortion justified the use of deadly force against Tiller.
Tiller, 67, was one of the few U.S. doctors who performed late-term abortions. He had already survived one attempt on his life and a clinic bombing before he was slain.
During Roeder's testimony Thursday, Tiller's widow, Jeanne, and other family members sat in the gallery. Initially stoic, they began to dab at tears as Roeder described putting a gun to Tiller's head.
Asked if he regretted what he did, Roeder said, "No, I don't." Upon learning that Tiller's clinic was shut down after his death, he said he felt "a sense of relief."
Dressed in a dark suit, white shirt and a red patterned tie, Roeder calmly testified that he had a long-standing belief that Tiller should die.
He thought about different ways to kill the doctor -- driving a car into him, perhaps, or shooting him with a rifle. His main concern, Roeder said, was that he might harm others.
Under cross-examination by Sedgwick County District Attorney Nola Foulston, he said he also considered cutting Tiller's hands off with a sword, but decided that would not be effective, as Tiller would still be able to train others.
Roeder said that through the anti-abortion group Operation Rescue he learned that Tiller took measures to protect himself -- traveling in an armored car, using a security escort, wearing a bulletproof vest and living in a gated community.
He decided to kill Tiller at his church, he said, because "I felt that actually if he was to be stopped, that was probably the only place he could have been stopped. ... It was the only window of opportunity I saw."
Roeder said he visited the church four or five times before Tiller's death. The week before the shooting, on May 24, he carried a .22-caliber handgun with him, he testified, but Tiller did not attend church that day.
On May 31, though, the doctor was greeting congregants in the foyer of Reformation Lutheran Church before Roeder walked up to him and shot him at point blank range.
"The lives of those children were in imminent danger if someone did not stop George Tiller," Roeder said. "I shot him."
Under questioning from Foulston, Roeder acknowledged that he "somewhat" admired those who previously had committed violence against abortion providers.
He said his anti-abortion beliefs "go hand in hand" with his religious beliefs. He said he became born again in 1992 after watching an episode of "The 700 Club."
Asked if there are any circumstances in which he believes abortion is acceptable, Roeder said he thought it could be if the mother's life was in "absolute" danger.
"I struggle with that decision," he said, "because I believe that ultimately, it is up to our heavenly father. But if there was a time, that would be it."
He said he did not believe abortion was justified in the case of rape.
"You are taking the life of the innocent. You're punishing the innocent life for the sin of the father. Two wrongs don't make a right."
Asked about incest, he said his beliefs were the same: "It isn't our duty to take life, it's our heavenly father's."
Roeder's testimony was peppered with objections from prosecutors. Many objections were sustained by Wilbert, who has maintained he does not want the trial to become a forum on abortion.
In a conference out of the presence of jurors, Wilbert cautioned Roeder, saying specifics on medical procedures would not be allowed. Roeder's testimony would proceed, Wilbert said, "on a question-by-question basis."
Roeder recounted conducting what he called "sidewalk counseling" at Kansas City abortion clinics, handing pamphlets and other literature to women as they went inside. "Some of them did ultimately change their mind," he said.
In opening statements Thursday, defense attorney Steve Osburn told jurors Roeder "killed Dr. Tiller because he believed that was the only way, necessary to save the lives of the unborn."
Defense attorneys claim Roeder was also motivated by authorities' failure to punish him through the judicial system.
Wilbert refused to allow former Kansas Attorney General Phill Kline to testify on behalf of the defense. On Wednesday, he refused to allow testimony from current Deputy Attorney General Barry Disney. Kline unsuccessfully attempted to prosecute Tiller in 2006. Disney charged Tiller with 19 misdemeanor counts, but a jury acquitted the doctor.
Wilbert said Roeder can testify about the cases and how they affected his beliefs, but to allow testimony from Kline would "get into legal matters that do not concern this jury."
And, the judge said, the cases do not give Roeder a basis to state absolutely that Tiller's actions were illegal, since the doctor had never been convicted.
Roeder testified he was "very frustrated" by Tiller's acquittal, saying it "seemed like that was the last attempt by the state of Kansas to find if there was anything at all going on illegally in George Tiller's clinic."
Randall Terry, founder of Operation Rescue, told reporters outside the courtroom the trial is "a railroad, a kangaroo court, where they are denying critical evidence about what was on Scott Roeder's mind when he pulled the trigger."
"Perhaps if the Sedgwick County prosecutors had done a better job prosecuting Tiller for how he illegally killed babies, he would still be alive," Terry said.