A 25-year-old man has been charged in the murder of Simon Fraser University professor Melanie Alexis O'Neill, whose body was discovered last summer in her Vancouver home.

Matthew James Scott was taken into custody Saturday and charged with one count of second-degree murder. He remains in custody and is scheduled to appear in court Wednesday.

O'Neill's body was discovered in her triplex in the 100-block of West 13th Avenue last July 26. Police believe the popular 37-year-old chemistry professor was killed four days earlier, though the cause of death hasn't been released.

Insp. Brad Desmarais said Scott and O'Neill were in an "on again, off again relationship," and that the accused sometimes stayed at her home.

"The exact details of the relationship will be relevant to the trial so we can't get into it too much," Desmarais added.

Police say Scott is unemployed and initially met O'Neill as an acquaintance.

The seven-month investigation of O'Neill's death eventually ballooned to involve 40 officers from multiple jurisdictions including Vancouver, Port Moody, Delta, Saanich and Victoria, as well as members of the RCMP Behavioural Sciences Unit.

O'Neill graduated with a PhD at Dalhousie University in 2001 before doing her postdoctoral fellowship at the California Institute of Technology from 2001 to 2004.

She had worked at SFU for six years when she died.

Police described the professor as a "brilliant young scientist" whose death was a loss to her family, friends and the academic community.