A man who admitted to sexually assaulting and killing an elderly Hawkesbury woman eight years ago is going to jail for at least 20 years.

Robert Brunet, now 63, broke a window and entered the home of 81-year-old Violet Graves before strangling her to death in July 2000.

Justice Robert Maranger called the killing "brutal" and "vicious," sentencing Brunet to life in prison with no chance of parole for 20 years.

Brunet appeared in court to start his testimony last week but the trial ended abruptly with his admission of guilt on Sept. 9.

Instead of continuing with the trial, Brunet told his lawyers he wanted to plead guilty to a second-degree murder charge.