Stripped of his Unabomber mask, Theodore Kaczynski faces sentencing Monday not as a crusading anti-technology environmentalist but as an embittered, unbalanced revenge killer.

Under a plea bargain hammered out on the eve of opening statements in January, a federal judge is scheduled to sentence the 55-year-old former math professor to four life terms in prison plus 30 years for killing three men and maiming two others.Kaczynski is expected to be sent to a high-security federal prison, defense attorney Quin Den-vir said.

A half-dozen of his victims or their family members are prepared to address U.S. District Judge Garland Burrell Jr. in the hope of bringing some closure to the losses they suffered.

Whether Kaczynski will speak, not even his own attorneys can say.

"I don't know what he'll do," Denvir said. "I think it's unlikely, but with him, you never know."

Kaczynski's 18-year bombing campaign changed the way Americans mail packages and board airplanes, and at its height in July 1995 virtually shut down air travel on the West Coast.

In his Unabomber manifesto, Kaczynski claimed a moral high ground, justifying the attacks in the name of preserving humanity and nature from the relentless onslaught of technology and exploitation.

But the journals found by FBI investigators in his Montana mountain cabin instead revealed a cynical, apparently sexually confused killer who delighted in his bloody explosions and cared little for the outside world.

Environmentalist? Hardly.

"I believe in nothing," Kaczynski wrote. "I don't even believe in the cult of nature-worshipers or wilderness-worshipers. (I am perfectly ready to litter in parts of the woods that are of no use to me - I often throw cans in logged-over areas ...)"

His real reasons for killing were simple.

"My motive for doing what I am going to do is simply personal revenge," he wrote.

One journal entry spoke of Kaczynski's reaction when, in graduate school at the University of Michigan in 1966, he visited a psychiatrist to discuss the possibility of a sex change operation.

Too ashamed to talk of his confused sex life, he left the meeting and wrote in his diary: "Why not really kill that psychiatrist and anyone else whom I hate."

Since his brother David's tip led to Kaczynski's arrest in April 1996, the family has claimed the writings were that of a paranoid schizophrenic, not a cold-blooded killer. In January a federal prison psychiatrist agreed, opening the way for prosecutors to drop their demand for the death sentence and allow the plea bargain.

Anthony Bisceglie, a lawyer who represented David Kaczynski, claims no victory in helping to save Ted Kaczynski from lethal injection.

"There were two possible endings to this story - one was sad and one was horrific. We aimed for the sad ending," Bisceglie said. "The upside is that there will be no more killing and that Dave was able to save one more life. The downside is that Ted was convicted but he was not cured. The delusions that led to his actions remain."

But prosecutors see not the sympathetic face of a mentally ill genius, but a killer cold enough to freeze the blood.

In court documents, they recounted the agonizing deaths of his victims and the horrific effects of the bombings on the victims.