Dellen Millard, 37, who was previously convicted of the first-degree murders of Tim Bosma, Laura Babcock and his own father Wayne Millard, was convicted of assault causing bodily harm Monday in the Ontario Court of Justice in Napanee.
Justice Geoffrey Griffin found him guilty in connection to the stabbing of a fellow inmate, Sean Trites, at Millhaven Institution.
The stabbing left Trites with his shirt torn and blood-soaked, cuts to his neck and left shoulder and a puncture wound to his abdomen, according to court records.

Millard and another offender, Clayton Sumner were charged after the stabbing at Millhaven on July 11, 2021.
They each also faced a charge of possessing a weapon, which was “a 3.5-inch, jail-made metal stabbing weapon.
Sumner entered a guilty plea for the assault charge, but Millard pleaded not guilty to both charges.
Millard represented himself at trial and called several witnesses, including Trites.
The judge said the footage also shows Millard “controlling Mr. Trites’s movement as Mr. Sumner continues the punch-stab motions to Mr. Trites’s torso area.”
“I am satisfied beyond any reasonable doubt that when Dellen Millard got behind Mr. Sean Trites while Mr. Clayton Sumner was attacking … and Mr. Millard with his arm took control of Mr. Trites’s body, thereby compromising Mr. Trites’s ability to move away from the attacking Mr. Sumner with his weapon, that Mr. Millard was party to the offence of aiding Mr. Sumner in the assault causing bodily harm,” Griffin read from his decision.
Sentencing is set to take place on April 27.