I think the OP is right to be wary.
It might be that the killer has multiple personalities as his identity disorder or he might identify as the opposite sex.
If the latter, as is well proven by now, what with specific campaigns being set up to not record men's crimes as committed by women and the Keep Prisons Single Sex campaign, men can just Self ID into women's prisons.
Violent crime is overwhelmingly committed by men so this man in particular could say he was a woman and be moved into a prison with women, maybe even one with a mother and baby unit.
It's not an unreasonable concern to have and I share it too.