I've seen JB referred to as a 'chicken' and a 'coward.' We can't understand psychopaths because we evaluate them through the lens of our own motivations, values and emotions. This is a fundamental mistake.
Psychopaths aren't cowards, they are just hungry. Like a lion is to their prey.
So whose descriptions are you willing to believe and accept?
And whose will you ignore?
The house keeper for example said the whole family got on and she never saw an argument. Colin expresses the problems between Sheila and her mother - but not anything substantial about Jeremy and his family - only that he had problems at school ( that probably applies to 50% of the population)