James Kopp wants his murder trial to be a referendum on abortion, but that strategy has failed other activists who stood trial for anti-abortion shootings.

Since 1993, juries in the U.S. have convicted three men and one woman of murder or attempted murder of clinic workers. All the cases stemmed from a violent 21-month period in the mid-1990s that left two doctors, two receptionists and a volunteer dead, and seven others wounded.

In two Florida trials, judges severely limited defenses related to the abortion cause. In a Kansas case, the jury appeared to reject a nullification defense, and in Massachusetts, the defendant claimed insanity, but was convicted anyway.

Kopp, who faces second-degree murder charges for the 1998 shooting death of obstetrician Barnett Slepian, could receive up to 25 years if convicted.

Michael Griffin: Brainwashing defense

Navy veteran Michael Griffin was the first activist to kill. On March 10, 1993, he broke away from other anti-abortion picketers outside the Pensacola Women's Medical Services clinic, pulled a .38-caliber from his pants pocket, and shot David Gunn, a doctor working at the clinic, several times.

Michael Griffin

Originally, he planned to tell jurors that he had been brainwashed by the most radical facets of the anti-abortion movement. Specifically, his lawyers cited "poison" movies of mutilated fetuses and pamphlets that seemed to encourage violence, and said such materials fomented a madness in Griffin that "may well have induced the defendant to agree to a form of martyrdom."

The trial judge, however, refused to allow the testimony because Griffin would not agree to psychiatric exams.

Griffin did not testify, but his lawyers argued that he was not the mastermind and was perhaps covering for others in the movement. A jury convicted him in less than three hours and the judge sentenced him to life in prison.

Rachelle Shannon: No remorse

Oregon mother Rachelle Shannon once praised Griffin as "the awesomest, greatest hero of our time." She traveled to Kansas to protest at the Women's Health Care Services clinic in Wichita and in Aug. 19, 1993, she shot Dr. George Tiller twice, once in each arm, with a semiautomatic pistol.

Rachelle Shannon

Tiller was only slightly wounded and returned to work the next day. At her trial, Shannon first claimed that she was only trying to injure Tiller to prevent abortions. She shocked even her lawyer, however, when, during 90 minutes on the witness stand, she said there was nothing immoral about killing Tiller and acknowledged trying to make bail so she could bomb the clinic to stop the doctor's work.

The jury quickly convicted her of attempted murder and she was sentenced to 11 years in prison. At her sentencing, she said, "It would be hypocritical to pretend like I did something wrong when I know I didn't."

Paul Hill: Copycat crime

Former Presbyterian minister Paul Hill was one of many anti-abortion protesters to attend Michael Griffin's trial. He later said Griffin's actions inspired him to kill. Early on the morning of July 29, 1994, Hill went to Pensacola's other clinic, the Pensacola Ladies Clinic, and waited for employees to arrive. When John Britton, a doctor brought in to replace the murdered Gunn drove up with a pair of married volunteer escorts, Judy and James Barrett, Hill opened fire with a 12-gauge shotgun.

Paul Hill

Britton and James Gunn were killed and Judy Barrett wounded. As Hill was led away by officers, he said, "One thing for sure, no innocent babies will die in that clinic today."

Hill wanted to use a justifiable homicide defense, but prosecutors successfully argued that abortion, as a constitutionally protected right, is not a harm that could justify a killing.

Hill, who represented himself, did not put on any evidence or make a closing argument. A jury convicted him in 20 minutes and a judge later sentenced him to death.

John Salvi III: Paranoid schizophrenic

Former hairdresser John Salvi III went on a shooting spree in Brookline, Mass., on Dec. 30, 1994 . He fired on two clinics, killing receptionists Shannon Lowney and Lee Ann Nichols, and wounding five others.

John Salvi III

At his trial, his defense said Salvi was a paranoid schizophrenic who did not understand his actions at the time of the shooting and should be found not guilty by reason of insanity.

Prosecutors acknowledged Salvi had some mental problems, but claimed he was well enough to identify ideological targets, buy weapons, plan his attack and make an escape.

One witness testified that after killing Nichols, Salvi shouted, "This is what you get! You should pray the rosary!"

He was convicted of two counts of murder and sentenced to life in prison. He committed suicide in his cell nine months later.