HALIFAX -- Two former girlfriends of a Halifax man convicted in the violent death of a Montreal-born businesswoman and yoga instructor testified Friday at his parole eligibility hearing, describing him as controlling and prone to radical mood swings.

Nicholas Butcher was convicted of second-degree murder in April after a jury found he stabbed 32-year-old Kristin Johnston to death. The conviction carries an automatic life sentence, but a hearing was held to determine when Butcher will be able to apply for parole.

Crown prosecutor Carla Ball argued that Butcher should not be allowed to apply for parole for 17 years, noting what she described as Butcher's "forethought" for confrontation and that Johnston was his domestic partner -- considered a breach of trust and an aggravating factor under the Criminal Code.

But defence lawyer Peter Planetta said his client should be eligible for parole after 10 years, pointing to mitigating factors such as his clean record and prospects for rehabilitation.

Nova Scotia Supreme Court Justice Joshua Arnold reserved his decision until Aug. 22.

Submissions from the lawyers came after victim impact statements by Johnston's friends and family were read in court, describing the ongoing, devastating impact of her death.

A gut-wrenching video recording of her sister's victim impact statement brought many in the courtroom to tears.

Kim Johnston described Kristin's special relationship with her young niece, and the bond the two shared.

"The pain of that loss is harrowing, knowing that Kristin can't hold her anymore, lie with her for naps, sing to her and love her," she said, adding that her daughter was "robbed of the best auntie."

Kim Johnston was eight-months pregnant when Kristin was killed, and she said she worries about how her son was impacted by the tragedy.

"I think about how the actual DNA of my son was affected when I screamed out in terror every night until he was born, or when I sobbed myself to sleep," she said.

"My life has been completely devastated.... Everything that is supposed to bring me joy only brings sorrow. Our lives are changed forever for the worse."

Butcher stood in court at the end of the day to apologize to Johnston's family for what he called their "unbearable, incalculable and irreparable loss."

"I wanted to convey to Kristin's family that I'm so sorry beyond what words can express for being the cause of Kristen's death," he told the court. Butcher said he's spent "every waking moment" for the last two years wishing that "none of this had ever happened."

He was charged after police found Johnston's body next to a steak knife on a blood-soaked bed inside her Halifax-area home on March 26, 2016.

The jury heard that he called 911 and told the dispatcher he had killed his girlfriend and tried to kill himself. He also cut off his right hand with a mitre saw, but it was surgically reattached.

The Crown called two witnesses Friday to "highlight the character of the offender," Ball said.

Kathleen Byford-Richardson, his former girlfriend, described her relationship with Butcher as "very romantic," but said it became riddled with conflict.

She told the court he became anxious in social situations and controlling of her behaviour.

Byford-Richardson said she called Halifax police after Johnston's death, worried she had experienced a similar pattern of behaviour at the end of her relationship with him.

"I felt guilty I hadn't reported what I experienced at the time," she told the court.

She said she started dating Butcher in 2007 and they were together for about 2 1/2 years before she broke it off.

She claimed that during an argument he tried to push her from behind and spat on her at their shared apartment in Montreal.

After their breakup, Byford-Richardson said the two stayed in contact after he moved to Hamilton, Ont., for school in the fall of 2009.

A couple of months later, Byford-Richardson said he returned to Montreal and the two agreed to meet for dinner and a movie. After dinner, she told the court they drove to Parc Jean-Drapeau east of Montreal, where he presented her with a ring.

But when she declined to accept the ring, she alleged that his behaviour changed "radically."

Byford-Richardson told the court the situation became "unhinged" and she learned he had been lying to her about his time in Hamilton and the purpose of his visit to Montreal.

She said his "rapid speech" and "confessions" made her worried, and she asked him to take her home.

"No one knew where I was," Byford-Richardson said. "He was agitated, his hands were shaking."

Butcher's former girlfriend said she learned that he had been reading her emails and checking her Facebook account after their breakup.

The next day she said he began sending her insulting text messages, which she said were a "radical departure of how he'd been leading up to the night of the ring."

Byford-Richardson said out of concern for Butcher's safety, she called his mother in Halifax and later learned Butcher had been admitted to the psychiatric unit of a Montreal hospital.

The Crown also called a second witness, Olivia Hasler, who dated Butcher in Halifax from roughly 2013 to the spring of 2015.

Hasler told court Butcher would become depressed and have a hard time getting out of bed, and that he would become easily agitated during minor arguments.

She said he became uncomfortable and upset in social situations, once leaving a wedding reception because she hadn't paid enough attention to him.

The judge allowed the evidence presented by the two women to be considered by the court "on a balance of probabilities" to give a "full picture" of Butcher's behaviour. However, he said the evidence would not be used as an "aggravating factor."

Butcher's sentence of life imprisonment comes with a parole ineligibility period of between 10 years and 25 years.