SALEM — Two Salem police detectives who never gave up their search for a vicious rapist who tricked his way into a college student's apartment 18 years ago were praised yesterday by a judge and a prosecutor.

Thomas Crouse, a former Swampscott resident, pleaded guilty yesterday to the 1990 rape of a then-22-year-old Salem State College student in her Derby Street apartment and was sentenced to an 18-to-20-year prison term. The actual sentence doesn't matter much because Crouse is already serving a life term for the murder of a 14-year-old Malden girl.

But "at least (the victim) doesn't have to wonder who this person is, if he's still out there, if he could victimize someone else," Salem Superior Court Judge David Lowy said during yesterday's sentencing.

And that wouldn't have happened without the work of Salem police detectives James Gauthier and James Page, "who didn't give up on this case," Lowy said.

It was 18 years ago this week, on April 25, 1990, when the victim was returning to her apartment on Derby Street after a trip to Shaw's.

She noticed a man walking around with a walkie-talkie, prosecutor Gerald Shea told the judge. As she carried in her bags, the man approached, telling her he was a private investigator and that his car had broken down at Salem Willows. Could he use her phone to call a tow truck?

She let him in. As the woman looked through a phone book for a number, the man suggested he should just call police. He took the phone and appeared to dial a number, then told her the line was busy. He then appeared to make another call. Then he just stood there.

Suddenly, he offered her cocaine. When the woman refused, he lunged at her, pushing her onto her futon in the tiny studio apartment. The woman struggled, but Crouse pulled off her clothing and raped her.

Then he tied her up with her dog's leash and stuffed a dishrag in her mouth, warning her not to call police because he knew where she lived.

The woman eventually freed herself and went to police. She gave police a detailed description — a description that included her attacker's large panther tattoo on his thigh. Police also had the results of a rape exam done at Salem Hospital.

But the case grew cold. In those days before DNA analysis and before felons were required to submit DNA samples, Crouse was never a suspect.

Every time Gauthier and Page learned about someone with a similar tattoo being arrested, they would compare that suspect to the composite that the woman had provided. But Crouse never emerged as a suspect.

"We had put information (about the case) up and down the East Coast," Gauthier recalled yesterday, "looking for other cases."

A life of violent crime

Police later learned that soon after the Salem rape, Crouse was picked up in Fort Lauderdale, Fla., on a rape charge involving a tourist, who eventually decided not to pursue the case. A few years after that, he was convicted of a rape in Suffolk County and served prison time, according to court records.

Then, Crouse was convicted in the 2000 murder of a 14-year-old runaway girl from Malden whose body was found in a shallow grave in New Hampshire. As a result, his DNA was entered into a statewide DNA database.

But police never linked the former Swampscott man to the unsolved rape.

In 2003, Page was taking a class on DNA. The technicians who taught the course suggested that police submit evidence from unsolved cases.

Page said he knew the case had been bothering his partner for years. They submitted the samples and waited.

Then they realized that the 15-year statute of limitations was about to expire in the case. They made another call. And then they got word that there had been a "hit" in the state Combined DNA Index System.

Just to be sure, they got a new DNA sample from Crouse, who was serving a life sentence at Cedar Junction. They compared his photo to the composite sketch.

And they showed a photo of Crouse's panther tattoo to the victim.

They had their man.

'An extraordinary woman'

It would be a few more years until Crouse was ready to admit to the crime. He had nothing to lose, given that his murder conviction has already been upheld by the Supreme Judicial Court and he is serving a life sentence without possibility of parole.

But last year's publicity about problems at the state DNA lab led to motions by his lawyer seeking access to records of the facility and another delay in the case. The Crouse case was not one that was affected by the lab problems, Gauthier said.

Through all of those years, the victim stood ready to testify.

"She's an extraordinary woman," Gauthier said yesterday. He said he almost felt bad about getting in touch with her, fearing it would revive painful memories, when they first realized they had identified her assailant. But "she never lost faith," he said.

And both officers said yesterday they were amazed at the victim's capacity to show compassion.

In a victim impact statement, the woman, now 40 and a mother herself, said she believes Crouse wasn't born evil.

"We are all born innocent, and I know that someone must have done Thomas Crouse wrong at some point in his life," she said. "Because he couldn't have become the person that he has otherwise. ...

"Thomas Crouse, I pray that you find peace within yourself and heal enough to make your world inside prison walls a better place for you and everyone around you."

She also had praise for the detectives.

"Without their tenacity, I wouldn't be here today finally feeling some closure to this part of my life," she told the judge.

Lowy said he found the woman's strength and belief in the possibility of redemption "remarkable."

And he flatly rejected defense lawyer Carmine Lepore's request to give Crouse credit toward his sentence for the time he's been in custody since his indictment in the rape, saying there was "absolutely no reason for the court to provide any credit" given that he has been serving a sentence for murder.

Gauthier and Page hugged the victim as Crouse was led out of the courtroom.

"He's an evil guy," Gauthier said.