and his brother-in-law, Dennis Cheesman, were convicted of manslaughter in the deaths of four experienced
Mounties in 2009 and sentenced to 15 and 12 years in prison respectively.
The murders were committed by James Roszko in 2005. Roszko had terrorized the residents of Mayerthorpe for most of his adult life. Despite the numerous attempts by the RCMP to convict him for various crimes
including counselling to commit murder, sexual assault and other weapons related charges, Roszko generally managed to evade prosecution. At one point a judge attached a condition to his release that he stay away from the RCMP who, according to the Crown Prosecutor, reported that they thought he was following them.
Hennessey and his brother-in-law Dennis Cheeseman, were convicted of manslaughter after confessing to agreeing to Roszko’s demands for a rifle, ammunition and a ride back to his farm on the day prior to the murder. Hennessey said that he was afraid
for his safety and that of his wife and child if he refused accede to Roszko's demands.
is eligible for statutory release in December, 2015