English Law, its practitioners and judges are not necessarily congruent with either reality or what the medical profession consider to be a deviation therefrom.
A case in point is the trial of the Yorkshire Ripper whom the jury found to be not suffering from mental illness. After a short period of incarceration in HMP Parkhurst he was subsequently transferred to the secure mental hospital, Broadmoor, where he belonged for the next 30 years as a paranoid schizophrenic.