The jurors will be back for a fourth day on Friday.
Magnotta is charged with first-degree murder and four other charges in the slaying and dismemberment of Chinese engineering student Jun Lin in May 2012.
The eight women and four men began deliberating on Tuesday and have emerged just once because they wanted to know whether personality disorders are considered a mental disorder under law.
Quebec Superior Court Justice Guy Cournoyer told them Wednesday the answer to their question was yes.
Magnotta, 32, has pleaded not guilty by way of mental disorder and is seeking to be found not criminally responsible. His lawyer says he is schizophrenic and couldn't tell right from wrong at the time of the slaying.
Prosecutor Louis Bouthillier has argued the schizophrenia was a misdiagnosis and that his medical problems and behaviour are likely the result of personality disorders.
On the murder charge, the jury has four options: find Magnotta guilty of first-degree murder, second-degree murder or manslaughter, or find him not criminally responsible because of mental disorder.
The judge told the jurors Monday that if they find the accused not criminally responsible, that verdict must be the same for all five charges.
Magnotta is also charged with 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.