MONTREAL -- Luka Rocco Magnotta's father suffers from paranoid schizophrenia and suggested his son go see a psychiatrist because he was concerned about his mental well-being more than a decade ago.

The polite, soft-spoken 50-year-old man was the first defence witness to be heard at Magnotta's first-degree murder trial, describing his son on Friday as a "very mixed-up" child who was isolated and had no friends growing up. He suggested his son was abused by his mother's family.

Magnotta, 32, is charged in the slaying and dismemberment of Jun Lin in May 2012 in Montreal before he fled to Paris and then Berlin.

He has admitted to killing the Chinese engineering student, but has pleaded not guilty by way of mental disorder.

That defence began to take shape on Friday with the accused's father, who was diagnosed with schizophrenia and manic depression and saw traits in his son that raised concerns so he put him in touch with his psychiatrist in Magnotta's early 20s.

"In my opinion, he had problems for which he should seek help," said the father, whose name is subject to a publication ban.

He said Magnotta is the oldest of three children and that he and his brother bore the brunt of the abuse from their mother's family, who they lived with for a time after the marriage ended.

The father noted he was estranged from Magnotta's siblings -- a younger brother and sister he hasn't seen in about a decade.

"They were very mixed-up kids in all ways and they still are," said the witness, who was accompanied by a support person as he spoke while seated on a cafeteria chair in the witness box.

The father said Magnotta was home-schooled until he was in Grade 6 or 7 but was poorly taught by his mother. He testified he didn't agree with home schooling.

"She was very clingy, she wanted to have total control over them," he said of the woman. "In my opinion, she didn't do a very good job.

"He (Magnotta) had no friends, he was being home-schooled, no interaction with anyone . . . neither son did."

When Magnotta was finally enrolled in school, he was mistreated by other kids, said the 50-year-old Ontario man.

He spent his entire testimony referring to Magnotta by his birth name, Eric. The accused only changed it to Luka Rocco Magnotta about 10 years ago.

The father admitted he was offended by his son's decision to change his name.

"I couldn't understand why he would do that," the father said.

He testified his son's given names at birth, which the father chose, included Clinton and Kirk -- in reference to tough-guy actors Clint Eastwood and Kirk Douglas.

The father acknowledged having mental problems, which became apparent to him in the mid-1990s when his marriage to Magnotta's mother ended. It was after he stopped drinking that he realized the extent of his psychological issues.

"I heard voices, I felt like suicide, I felt angry," he said.

The man currently takes 29 pills a day including antidepressants and anti-psychotic pills. Before finding the right medication, he had countless visits to hospital emergency rooms for psychiatric trouble.

But with the medication, he's able to lead a normal, healthy life.

Soft-spoken and polite, the father admitted he still hears voices -- two or three voices, which are older, male and English-speaking. He said the voices would remind him to make sure no one comes near him or hurt him and pushed him to try to commit suicide. He described the feelings of paranoia and fear of being attacked as part of his illness.

"Your thoughts, feelings and emotions are all jiggled together," he said. "You hear voices and they tell you what to do."

The father's 1,700 page medical file was entered into evidence by defence lawyer Luc Leclair.

Under cross-examination from the Crown, the father said there was a roughly five-to-10 year gap where father and son did not speak as Magnotta was closer to his mother's family, who hated the father. He claimed his maternal grandmother was particularly taken with him and smothered, babied and favoured Magnotta.

Prosecutor Louis Bouthillier asked if there was a different reason for the gap: that Magnotta had allegedly had an affair with his father's new wife.

The witness denied the claim, saying it was a fabrication by a woman who didn't like him and his wife. He confronted his son about it, who denied it.

Bouthillier also asked about a visit to Montreal before his son's arrest where Magnotta had told him that he'd lived in Russia teaching English at a university and had a Russian wife named Oksana. The father said Magnotta often mentioned travelling a lot -- Russia, Italy, Florida and California among the places he'd been.

"That's what he said," the witness replied, having never seen proof or meeting the wife Magnotta later told him he'd split from.

The father said he met with Magnotta after his June 2012 arrest, visiting him several times while he remained detained in Montreal. He says they discussed how he was feeling but never broached guilt or innocence with his son.

"I know that he didn't do it, this is from my own feeling," the father said.

Magnotta's father currently works as a cleaner after losing his job as a snack cart operator. He said he's working to have a criminal conviction spanning nearly two decades expunged so he can work as a security guard.

"God Bless you," the father said as the judge dismissed him at day's end.

Magnotta faces four charges in addition to premeditated murder: criminally harassing Prime Minister Stephen Harper and other members of Parliament; mailing obscene and indecent material; committing an indignity to a body; and publishing obscene materials.

The trial resumes Monday.