Toronto police said Friday they have arrested Ernest William Westergard in the 30-year-old murder of Donna Proian, a University of Toronto secretary who was stabbed and strangled in her downtown apartment in 1981.

Proian, 30, was found dead in her penthouse apartment at Village by the Grange, a condo-style building adjacent to the Ontario College of Art and Design University.

Her husband last saw her at 8 a.m. on June 23 of that year, and returned to their home to find her dead at 11:30 a.m.

Police said Westergard had been arrested at the Warkworth Penitentiary where he was being held for an unrelated murder.

The suspect was previously been convicted of another first-degree murder, the 1994 killing of Sonia Run. The 47-year-old woman had been strangled and sexually assaulted.

According to a list of women killed by their partners compiled by the Kingston Frontenac Anti-Violence Co-ordinating Committee, Run had been Westergard's girlfriend. He was sentenced to 20 years without parole in 1998.

Police credited advancements in technology and criminology for the new arrest, and officers issued a direct warning.

"You may think that you have gotten away with a homicide, but you haven't and you won't," said Det. Sgt. Steve Ryan.

"The scientific technology is so great that we will catch you. It may take time -- in this case 30 years -- but we will catch up to you. It's a credit to the investigators and it's a credit to the scientists."