Mary Frances Iaconis Lindgren, 67, was found brutally beaten, raped and murdered inside her bedroom at an assisted living center in Covina on Jan. 19, 1996.
Detectives at the time said they conducted a thorough investigation, interviewing facility workers, residents and anyone else connected with the facility but were unable to come up with a suspect.
They processed DNA found at the scene and entered it into state and federal criminal justice databases but did not find a match.
Then last year authorities took another crack at the case, sending the DNA to the state Department of Justice.
Last month, they got word back of a match.
Using the results, they identified David Adolph Bernal, 46, of El Monte as the suspect. He was arrested Thursday for the murder of Mary Lindgren.
His bail was set at $2 million and arraignment is expected Friday.
Lindgren's family members said they were relieved that her killer was finally caught and they credited the Los Angeles County Sheriff's Department for not letting the case go.
"We are profoundly grateful that the killer of our mother, Mary Frances Iaconis Lindgren, has been identified and arrested," said the statement from her children. "Haunted by her brutal murder for nearly two and a half decades, we are relieved to know that justice will finally be served."