The Crown stayed a second count against Nelson Hart of assaulting a peace officer before provincial court Judge Lois Skanes delivered her verdict.
Crown attorney Mike Murray said the assault charge, laid after Hart allegedly threw a paper plate and plastic cutlery toward three guards without hitting anyone, had become a distraction.
The incident happened as Hart was held in segregation at Her Majesty's Penitentiary on Jan. 30, 2013. At the time, his first-degree murder conviction in the 2002 drowning deaths of his three-year-old twin girls had been overturned but he was still behind bars pending an appeal.
Skanes ruled Hart meant to intimidate when he said, referring to one of the guards: "First chance I gets, I'm going to stab him up."
"Hart was clearly agitated and angry when those words were spoken," Skanes said in her decision.
The judge said testimony from two of the three correctional officers who were at Hart's cell convinced her his words met the legal test for conviction. Namely, that a reasonable person in the circumstances would have considered them a threat of bodily harm.
Still, Skanes said it was "unfortunate" that the police officer who charged Hart the next day did so without taking statements from the guards. Nor did Const. Cody Dunphy of the Royal Newfoundland Constabulary review security video of the incident prior to laying the charges, he confirmed Tuesday in court.
Two correctional officers testified that Hart suddenly became irate and told the third guard he would stab him.
Krista Williams said Hart threw a paper plate and plastic cutlery at them when they tried to confirm he'd swallowed the medication they had just given him. Williams said Hart found the protocol "demeaning." It required inmates to show their open mouths to prevent prescription drug hoarding and abuse.
The third guard who was present that day did not testify Tuesday.
Hart had pleaded not guilty to both charges he originally faced.
The case returns to court on Feb. 27 to set a date for sentencing.
Hart, 46, has been free since the Crown decided last August it lacked enough evidence to retry him for murder in the deaths of his daughters at Gander Lake.
A Supreme Court of Canada ruling last July found that confessions Hart made to police posing as gangsters during a so-called Mr. Big sting were inadmissible. It said those tactics were extreme and potentially infringed Hart's Charter rights. It also cast doubt on the reliability of evidence drawn from similar investigations across Canada.
The top court judgment affirmed a 2012 appeal court decision overturning Hart's 2007 murder conviction and life sentence.
Follow @suebailey on Twitter.