Warning: This article contains disturbing details that may be triggering for readers. The murder trial of a Muskoka prisoner, already serving a life sentence for murdering his girlfriend, is entering its final week. Devon Saunders, 57, arrived at the Bracebridge courthouse Thursday where a jury will soon decide whether Saunders acted in self-defence the night he killed his former cellmate Leslie Ma at Beaver Creek Institution in Gravenhurst. READ: Muskoka prison murder trial for inmate serving life sentence for girlfriend’s murder: 2008 Saunders, who was convicted in 2015 of the first-degree murder of his girlfriend Shernell Pierre nearly 20 years ago, stabbed Ma several times on the night of Dec. 18, 2022, when the Crown alleges Saunders used a rock to first strike Ma in the head in a common area, before killing him in the neighbouring kitchen. Within moments, the court heard, a fellow inmate told guards to call an ambulance. Correctional officers discovered Ma leaned up against the kitchen cabinets with his head slumped forward and blood coming from his front and side torso. Attempts to save his life were unsuccessful and Ma never regained consciousness. The Crown alleges Saunders planned and carried out to the murder while the defence argues the accused argues he feared for his life in months, following threats from Ma and his friends inside the prison, that they were going to kill Saunders. The defence told the jury, during its opening remarks, that Ma had a “beef” with Saunders over one of his associates at a Manitoba prison where they had both done time. Saunders, the defence argues, had been previously assaulted by a group of men in the shower. The court heard Saunders and Ma were cellmates for about three months in Gravenhurst until Ma was relocated six months prior to his death. Saunders was convicted of murdering his girlfriend, Shernel Pierre, who was shot in the head inside her car that was later found burned near the West Edmonton Mall. Saunders was interview by police following her death but was not arrested until four years after Pierre was killed. Saunders has maintained his innocence, hoping to one day overturn his murder conviction. The trial, before Regional Senior Judge, Justice Howard Leibovich, enters its third and final week on Monday when it is expected the defence will call its first witness to the stand.