Documents made public by the Quebec Court of Appeal on Monday outline several reasons for Magnotta's attempt to have the five convictions annulled, including the one for killing Lin.
The appeal centres primarily on a number of instances in which the defence suggests the judge erred in the case.
After a lengthy trial, jurors deliberated for eight days before finding Magnotta guilty on Dec. 23 of premeditated murder and four other charges in Lin's slaying in May 2012.
The first-degree murder conviction carried a sentence of life imprisonment with no chance of parole for 25 years.
Magnotta, 32, was also given the maximum sentences on the four other charges.
The documents filed by Toronto-based lawyer Luc Leclair state Quebec Superior Court Justice Guy Cournoyer erred in a number of instances.
"The verdicts are unreasonable and unsupported by the evidence and the instructions," one of two motions filed by Leclair read.
One motion is a direct appeal of the convictions based on questions of law and could take many months to be heard.
In it, the defence argues Cournoyer erred by:
— including an instruction to the jury on motive that confused the issue of intent, planning and deliberation, all while failing to tell them motive had to refer specifically to Lin's murder.
— failing to instruct jurors on a limited use of "bad character" evidence relating to Magnotta.
— limiting the number of subjects to be covered in surrebuttal — rebuttal to the Crown's own expert rebuttal witness.
— and allowing the jury to discuss the case from the onset instead of waiting until after closing submissions and final instructions were complete.
Leclair also argues Cournoyer erred in instructions he provided on the Section 16 mental disorder defence Magnotta employed.
In the second motion, Magnotta is seeking leave to appeal on questions of "mixed fact and law" which will require the authorization of the province's highest court to go forward.
A spokesman for Quebec's director of criminal and penal prosecutions says the appeal doesn't come as a shock.
"For the moment it's not a surprise for us because the accused was convicted of first-degree murder, so it's usual that the accused appeals that kind of infraction and that kind of conviction," Jean-Pascal Boucher said in an interview.
The appeal is likely months away as transcripts need to be filed and the prosecution must also submit its reply to the appeal.
"For the moment, we won't talk about the legal problem invoked by the appellant," Boucher said. "We will have to do that in our factum."
A prosecutor specializing in appeals will likely take on the case, Boucher said.
"They are specialists in that kind of case so we'll see in the next few weeks who will be the prosecutor in this fight in front of the Quebec Court of Appeal," he said.
The appeal documents were dated last Thursday and include a notice that a hearing will take place in Montreal on Feb. 18.
Leclair denied to comment further when reached by telephone.
Magnotta admitted to killing and dismembering Lin but was seeking to be found not criminally responsible by way of mental disorder.
Psychiatrists who testified for the defence said he was in a psychotic state the night of the killing and couldn't tell right from wrong.
The Crown countered the crime was planned and deliberate and that Magnotta's behaviour and actions were incompatible with those of someone supposedly suffering from a disease of the mind.
The jury heard testimony about the gruesome details of Lin's death and that many of Magnotta's actions were caught on surveillance video or in images taken by the accused himself.
They also heard about Magnotta's upbringing and delved into medical files that showed he was diagnosed with schizophrenia in 2001.
In the roughly 48 hours following the slaying, Magnotta cut up Lin's body into 10 pieces, mailing the hands and feet to political offices in Ottawa and primary schools in Vancouver. He also bought a plane ticket for Paris online.
When police put out a warrant for his arrest, Magnotta emptied his bank accounts and fled to Berlin on the same day.
He was ultimately arrested in an Internet cafe in the German city on June 4, 2012, where a witness said Magnotta was reading up on himself.
He was eventually transferred to a Berlin prison hospital, where a psychiatrist's initial diagnosis was that he was psychotic.
The other charges Magnotta was convicted of were 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.
A Montreal lawyer representing the Lin family says they have been informed of the appeal.
Daniel Urbas said the family had inquired after the verdicts about a possible appeal. He told them Cournoyer was "experienced, talented and careful" and regularly sought consensus from both prosectuion and defence.
Urbas said the family were reassured that the consensus "eliminated most any grounds of appeal for the decisions he had to take."