WOBURN, Mass. (WHDH) -- Police solved a cold case in Lexington. 45-year-old Craig Conkey pleaded guilty to the 1992 murder of a 33-year-old woman.

Investigators said new forensic evident helped them solve the case.

He was sentenced to life in prison.

He admitted to breaking into Kathleen Dempsey’s home, waking her up and stabbing her to death. Dempsey’s family said they are happy justice was served.

“I won’t call this a happy day, obviously it’s not a happy day. It's a day we longed for for 20 years. We now know who did it and why,” said Evelyn Tobin, the victim’s mother.

Conkey is already serving another life sentence for murder.