Matthew de Grood, 23, has already been found fit to stand trial, but the Crown wanted a mental review to determine if he could be found criminally responsible if convicted.
Court heard Thursday that the report will be ready by de Grood's next court appearance set for Sept. 26.
De Grood, who appeared via closed-circuit TV from Edmonton, said nothing.
"We got word from Alberta Hospital from the forensic psychiatrist that she required more time to ... determine her opinion if there's criminal responsibility or not criminally responsible," said Crown prosecutor Neil Wiberg.
"As a result of that request, the matter will be next in court on Sept. 26."
De Grood was charged in April with first-degree murder in the stabbings at a party near the University of Calgary to mark the end of the school year.
A preliminary hearing has already been scheduled to begin March 2. No matter what the psychiatrist's report says, the hearing will go ahead unless the defence decides to waive its right to it.
"To my knowledge, no matter what the finding will be, this matter will proceed to preliminary inquiry and trial," said de Grood's lawyer Allan Fay.
"Ultimately we have to get a judge's ruling as to whether he was criminally responsible at the time."
De Grood, the son of a senior Calgary police officer, has been in psychiatric care since his arrest.
"When I last spoke to him he seems to be doing all right, as well as one can expect under the circumstances," said Fay.
"His parents are doing as well as one would imagine under the circumstances. They've been up to Edmonton on a number of occasions to visit him so they are appreciative of that opportunity."
De Grood is to remain in Edmonton until Sept. 19 and then transferred to the southern Alberta psychiatric unit prior to his next court appearance.
Police have not said what they think motivated the attack, but say de Grood was invited to the party April 15 and mingled with guests before violence broke out.
Zackariah Rathwell, 21; Lawrence Hong, 27; Joshua Hunter, 23; Jordan Segura, 22; and Kaiti Perras, 23, were slain.
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