In 1995 after David Kaczynski read the anti-technology manifesto of the Unabomber -- a mysterious mailbomber wanted by the FBI for nearly two decades -- he recognized the writings of his older brother, Ted.

The idea that his brilliant yet increasingly isolated brother could commit murder was beyond belief, David Kaczynski recounted Tuesday to more than 220 attendees at the University of Tennessee at Chattanooga's University Center.

"I was literally considering the possibility that my brother was the most wanted man in America," he said.

Under a plea deal, Ted Kaczynski was spared the death penalty based on his diagnosis of paranoid schizophrenia, and he now is serving life in prison without parole.

But David Kaczynski argued Tuesday that justice is not applied equally.

In 1999 California executed a decorated yet traumatized Vietnam War veteran, who'd been turned in to police by his brother, Bill Babbitt.

On Tuesday Bill Babbitt said he'd hoped his brother -- who had post-traumatic stress disorder and paranoid schizophrenia -- would receive treatment for his mental illness after he assaulted an elderly woman, who then died of a heart attack.

But Manny Babbitt spent 20 years in prison before he was executed in California on his 50th birthday.

The speakers pressed for a criminal justice system that recognizes people with severe mental illness are more likely to make false confessions and more commonly fire their lawyers and represent themselves in court.

Advocates with the National Alliance for Mental Illness in Chattanooga urged attendees to support a bill in the Tennessee General Assembly to exclude people with severe mental illness from facing the death penalty.

Amnesty International estimates that 10 percent of people who have been executed in the U.S. have serious mental illness, David Kaczynski said.

"I was always a believer in the death penalty ... until it came knocking on my door," Bill Babbitt said.

Contact staff writer Emily Bregel at ebregel@timesfree press.com or 423-757-6467.