requested such an opinion in Dr. Nussbaum’s retainer letter. The
applicant complains that Dr. Nussbaum did not report on this
question but rather confined himself to the physical maturation
of the structures of the brain.
 I do not accept this criticism.
 Dr. Chaimowitz and Dr. Martin, both of whom provided
affidavit evidence tendered by the applicant based their opinion
that administrative segregation would be difficult for persons
between 18 and 21 on the fact that their brains are still maturing. Dr. Nussbaum agreed that brain maturation continues until
people are in their 40s; he offered the opinion that the claim that
the brains of persons between 18 and 21 were fragile due to their
continued maturation beyond the age of 21 was overstated.
 In short, I am satisfied that Dr. Nussbaum drew a valid
distinction between his views and those of Dr. Chaimowitz and
Dr. Martin on this question.
 I accept the distinction drawn by Dr. Nussbaum and
found his evidence on this question persuasive.
 I am not satisfied that the evidence proves that, because
the brain of a person aged 18 to 21 continues to develop, that
person is vulnerable to severe termination of development if
exposed to administrative segregation.
 Accordingly, I would not, based on the evidence, conclude
that the legislative scheme permits cruel and unusual punishment or treatment because it does not forbid administrative segregation of persons between the ages of 18 and 21.
Inmates with mental illness
 The respondent to some extent agrees that inmates with
mental illness should not be in administrative segregation. The
dispute with the applicant arises in the definition of the class of
inmates with mental health issues who should be excluded from
 The August 1, 2017 revisions to Commissioner’s
Directive 709, at para. 19, provide that inmates
— with a serious mental illness with significant impairments
including inmates who are certified in accordance with pro-
vincial mental health legislation; and
— who are actively engaging in self-injury which is deemed
likely to result in serious bodily harm; or
— at an elevated or imminent risk of suicide;
— cannot be placed in administrative segregation.