WICHITA, Kan. — Rachelle Renee Shannon, a quiet, disheveled housewife from rural Oregon charged with shooting a doctor as he drove away from his Wichita abortion clinic last August, could hardly have made her attorney's job any harder.

Within hours of the shooting, Shannon was arrested, had confessed to police and had written a jailhouse letter to her daughter detailing her crime. As she was led away by police in the early morning hours, she turned to the waiting media and asked, on camera: "Did I get him?" She added to a police officer: "If ever there was a justifiable homicide, this was it."

Only later did she discover, to her dismay, that she had only wounded Dr. George Tiller in both arms and that he was back at work at his clinic the following day.

But Shelly Shannon, a self-described "puny wimp" and 38-year-old mother of two, simply couldn't keep her mouth shut, even when her court-appointed attorney told her to stop talking.

To her attorney's chagrin, she refused to plead not guilty by reason of insanity. No, she insisted, her mind had been clear. She knew what she was doing when she shot Tiller: She was a Christian attempting to stop a man who had made a career of murdering unborn babies. Shannon entered a plea of not guilty; in her mind, trying to kill a murderer is justifiable. And she wanted to get on the witness stand and tell the world what she had done. She was convicted March 25 and awaits sentencing on April 29.

She used the months before her trial to tell anyone who would listen about her life as an anti-abortion zealot and her earlier, previously unknown involvement in a string of abortion clinic bombings across the country. Later she admitted that she hoped to make bail before her trial so she could "blow up Tiller's clinic."

Shannon's willingness to talk has done more than call attention to her cause and clinch her conviction. She inadvertently triggered the first serious federal investigation into the question of whether an organized underground network of extremists is responsible for the wave of anti-abortion violence that has swept the nation in recent years.

For years, anti-abortion leaders have denied that they are behind the growing violence.

"There has never been a link between the violence and any responsible pro-life leader at all," said Patrick Mahoney, national spokesman for Operation Rescue.