ST. JOHN'S, N.L. -- The Newfoundland man whose murder conviction was thrown out over the reliability of Mr. Big stings is on trial in St. John's for allegedly threatening prison guards and assaulting them by throwing a paper plate and plastic cutlery.

Nelson Hart, 46, at times turned to look at reporters but declined outside court to comment as what was expected to be a two-day trial started Tuesday. It wrapped up early, and Judge Lois Skanes is to deliver her verdict Wednesday in provincial court.

Hart has been free since the Crown decided last August it lacked enough evidence to retry him for murder in the 2002 drowning deaths of his three-year-old twin girls in Gander Lake.

A correctional officer at Her Majesty's Penitentiary testified Tuesday that Hart seemed irate and told another guard he would "stab him up" during an incident two years ago.

Krista Williams said Hart threatened her and two male guards and threw a paper plate with some food and plastic cutlery at them on Jan. 30, 2013.

Williams said Hart, who has pleaded not guilty to uttering threats and assaulting a peace officer, became agitated after the guards gave him medication and asked him to open his mouth to show he'd taken it. She said it was protocol to ensure inmates weren't hoarding prescription drugs.

A three-minute video taken from prison security cameras was shown in court but had no sound.

The split screen on one side showed Hart pointing his finger and appearing to yell at the officers as he picked something up off the floor. On the other side of the screen, footage from another camera showed the officers standing at the opened door of Hart's segregation cell as at least two small, white objects sailed past them.

Under cross-examination by defence lawyer Jeff Brace, Williams said Hart had been temporarily moved to segregation because of various internal infractions, such as throwing blankets.

"Every day it was a constant struggle," she said of Hart's repeated refusals to show he'd taken his medication. Williams said he seemed to find the process, requiring him to open his mouth to show any pills were gone, "demeaning."

Correctional officer Stephen Woolridge also testified that Hart became furious that day.

"In a split second, he went from zero to 60," he said.

Brace suggested correctional officers were particularly hard on his client.

"Are we just hell bent on Nelson Hart?" he asked Woolridge under cross-examination before questioning whether Hart's response under the circumstances constituted assault.

Woolridge said objects thrown, especially when combined with threats, are considered assault.

"We wouldn't want to be beaten with a paper plate," Brace replied, prompting Crown lawyer Mike Murray to ask that he not be disrespectful.

Const. Cody Dunphy of the Royal Newfoundland Constabulary earlier confirmed under cross-examination that he charged Hart on Jan. 31, 2013, based on an unsigned, one-paragraph statement from a correctional officer without interviewing the complainants or reviewing the video.

"The decision was already made to charge him," Brace said.

Hart's 2007 conviction of first-degree murder in the drowning deaths of his daughters was overturned on appeal in 2012. The Supreme Court of Canada affirmed that decision last July, ruling that confessions Hart gave to undercover officers posing as gangsters during a so-called Mr. Big sting were inadmissible.

The top court cast doubt on the reliability of evidence gathered using such police tactics and said they may have infringed Hart's Charter rights.

The Crown withdrew any bid to retry the case last August, citing a lack of evidence.