You didn't say stupid you said thick as pigshit or mentally ill - now you widen out the definition? Based on what you know -
Baader Meinhof - terrorist attacks - thick / mentally ill participants or some other motivation?
Black September - Olympic attacks - thick / mentally ill or some other motivation?
IRA - Brighton Bombing - thick / mentally ill or some other motivation?
Jack Renshaw - the subject of this thread and his evil plans - bear in mind his defence has offered nothing in mitigation in terms of his intelligence or his mental state was he acting because he was mentally ill or thick as pigshit in your considered opinion?
and these two charmers?
https://www.bbc.co.uk/news/uk-england-birmingham-44467055
are they thick as pig shit or mentally ill - again not a defence tactic at the trial - maybe you missed your calling?