They embraced, fought back tears, and silently prayed.

Relatives and friends of Lena Bruce, the 21-year-old Tufts University graduate who was raped and murdered inside her South End apartment in 1992, struggled to maintain their composure Monday as her killer was convicted of first-degree murder, ending a 25-year quest for justice that had been stymied for decades before a DNA match broke the case open.

But two people were notably absent in Suffolk Superior Court as jurors rendered their verdict against 45-year-old James Witkowski — Bruce’s now-deceased parents, who went to their graves without ever knowing the identity of the man who assaulted and suffocated their daughter.

“My heart breaks for the parents of Lena Bruce, who never saw this day,’’ said District Attorney Daniel F. Conley after hearing the verdict.

He thanked investigators who worked the case, as well as Bruce’s sorority sisters and friends who “stood by her’’ and provided testimony at trial.

“As one of them said to me, ‘She would have done the same for us,’’’ Conley said.

Witkowski stood quietly in slacks and a loose-fitting collared shirt, showing no obvious signs of emotion as the verdict was read. His lead attorney, Daniel Solomon, declined to comment afterward, except to say that the case had been difficult.

Sentencing is scheduled for Thursday, and Witkowski faces a mandatory life term without the possibility of parole. All first-degree murder convictions are automatically reviewed by the state’s highest court.

Bruce’s relatives left without commenting.

They appeared tense before the verdict came down, with one female relative stifling tears, as another raised a palm skyward and whispered to herself with her eyes shut, apparently in prayer.

Another supporter loudly exhaled after the verdict, as Bruce’s friends and family hugged one another and later shook hands with police and prosecutors in the hallway.

Bruce had recently landed a job at an engineering firm and was living with a college friend at 694 Massachusetts Ave. during the summer of 1992, spending most of her free time with a tight-knit group of sorority sisters involved in community service, prosecutors and witnesses said.

Prosecutors said Witkowski, then 19, lived at a nearby homeless shelter and spent his days drinking at an area park.

One night in July 1992, he snuck into Bruce’s apartment, tied her wrists behind her back, “raped her, and killed her in her own bed’’ by suffocation, First Assistant District Attorney Patrick Haggan said during his opening statement, repeatedly pointing at Witkowski, who shook his head as he listened. “Her air passages were closed up for quite a while. Lena Bruce did not die quick. Lena Bruce died slowly.’’

For decades, Bruce’s killing went unsolved.

But a major break came in 2015, when Witkowski’s DNA sample, which he had to provide to authorities a year earlier for an unrelated conviction, matched DNA collected at the murder scene.

His sample was a match for semen found on Bruce’s body, as well as DNA found under her fingernails, Haggan said during his opening remarks. In addition, Haggan said, a slip of paper in a wallet found in front of Bruce’s apartment had a fingerprint that matched Witkowski’s.

Solomon had argued that the DNA evidence showed his client and Bruce had a sexual encounter at some point before the killing, but he insisted the government couldn’t prove Witkowski was in Bruce’s apartment at the time of the murder.

On Monday, Conley called for changes to Massachusetts law that would require suspects to provide DNA samples when they’re arrested for serious crimes, a requirement he said has been adopted by more than 35 states and the federal government.

Witkowski, Conley noted, was arrested several times for unrelated offenses during the years after the murder. Had the law been different, he said, investigators could have gotten a DNA match far earlier.

In a separate statement, Tufts thanked police and prosecutors for their work on the harrowing case.

“Lena Bruce was a talented, admired and much-beloved graduate of Tufts, and her tragic death in 1992 deeply shocked and saddened our community,’’ said Tufts spokesman Patrick Collins. “We hope that today’s verdict, and the knowledge that Lena’s killer has been brought to justice, will provide some solace and closure to Lena’s family, friends, and classmates.’’

Travis Andersen can be reached at travis.andersen @globe.com.