@PomandersandRedRibbon it hasn't been specified in the case, but if the defence team felt that there could be anything that would support the defence then they would request psychological or psychiatric assessments and reports to influence sentencing. That hasn't been mentioned so I assume he and the others have always been deemed to be of sound mind.
Sadly as much as we wish to look for unusual explanations, being cruel, having someone to blame/scapegoating, and enjoying having power over someone is not a particularly unusual thing. Unusual in the extent yes, but this is a situation that escalated over many years, and if unchallenged and abetted by others, I can see how it could get to this point. I mean, it's horrific and I don't for a second justify it, but, well, anyone on Mumsnet will have read plenty about the propensity of some to violence.