(CNN) -- After years policing Illinois streets for criminals, Drew Peterson is now among them -- and will be for more than three decades, a judge ruled Thursday.
Will County Judge Edward Burmila sentenced Peterson to 38 years in prison in the murder of his third ex-wife, Kathleen Savio, said state's attorney spokesman Charles B. Pelkie.
The former Chicago-area police sergeant will get credit for the nearly four years that he has been in custody, according to Pelkie, a spokesman for Will County State's Attorney James Glasgow. He could have received as many as 60 years in prison; Illinois does not have a death penalty.
"The reason that I never looked Drew Peterson in the eye is because I never acknowledged his existence," said Glasgow, describing the convict as a "cold-blooded killer."
"But I looked him in the eye today," the prosecutor said. "He knows that we did our job."
Peterson was convicted of murder in September but had fought for a new trial, an effort that Burmila denied Thursday, just before the sentencing.
Peterson's lawyers promised Thursday that they would press on with their appeal and expressed confidence they would prevail. They stood by their client, who defiantly claimed in court that he didn't kill Savio.
"Wouldn't you be angry if you were wrongly convicted?" said one of his attorneys, Steve Greenberg.
"In this case, (the prosecution) changed everything ... How would you feel if you were railroaded?"
Savio was found dead in her dry, clean bathtub on March 1, 2004. Prosecutors said Peterson killed her; the defense contended that she fell, hit her head and drowned.
The case did not grab headlines until after Peterson's fourth wife, Stacy, disappeared in October 2007. It was during the search for Stacy Peterson -- who still has not been found -- that investigators said they'd look again into Savio's death, which was initially ruled an accidental drowning.
Authorities altered their judgment and ruled Savio's death a homicide in February 2008, setting the stage for the first-degree murder trial last year of Peterson, a former police officer in Bolingbrook, Illinois.
A Will County jury ultimately convicted him of murder after nearly 14 hours of deliberation.
That was four months ago. On Thursday, all the parties were back in court to see whether Peterson would get a new trial or, if not, what his sentence would be.
Perhaps the most emotional part of this court proceeding was Peterson's long and emotional remarks, which were interrupted at times by shouts from Savio family members, several of whom were asked to leave the courtroom.
He unloaded "pent-up anger" that had built up over time -- against Savio and her family, the legal process, the media, even a TV movie about the case, according to his attorneys and the prosecutor. Above all, Peterson loudly insisted that he did not kill Savio.
Why was he upset? One of his lawyers, David Peilet, said part of it has to do with Peterson feeling the system that he served -- as a military veteran and longtime police officer -- had failed him.
"(He is angry) especially when you are somebody who has defended the Constitution and served and protected the public, now being faced with the same system coming up and biting (you) in the butt," Peilet said.
Glasgow, the state's attorney, had a different take. He called Peterson's remarks "pathetic," especially in how he "attacked" Savio and her mental state.
"Just depraved," the prosecutor said. "... We all got an opportunity to see a psychopath reveal himself in open court."
It was a sentiment echoed by the victim's sister, Susan Doman. She said she couldn't stand to hear "the devil" demean her sister, almost nine years after her death.
"He battered her to the very end."
Pam Bosco, a spokeswoman for Stacy Peterson's family, lauded the prosecution for making "this world a safer, better place" by fighting to convict Peterson and expressed hope he'd next be held accountable for what happened to his fourth wife.
"It's not over for us, but of course, a win for the Savio family is a win for the Stacy Peterson family," Bosco said. "We have a long journey ahead. We still want to see justice for Stacy. We won't give up."
Several Savio family members specifically mentioned Stacy when they addressed reporters late Thursday afternoon in Joliet.
Henry Savio Jr., a brother of Kathleen Savio, said Stacy Peterson's relatives "deserve the same thing that we're getting right now: justice."
As to Peterson's fate, Henry Savio said he wanted him to "stay in jail forever, to die there."
"(Then) he is going to go to hell," the victim's brother said. "And my sister is going to be watching him."
CNN's Elwyn Lopez, Carma Hassan and Michael Christian, from the InSession division of CNN's sister network TruTV, contributed to this report.