My feeling always with these kinds of cases is that we have to first consider whether the defendant's assertions are in any way credible. The prosecution does not have to disprove every wild theory from the defence.
In this case, I think the defendant is not at all credible, given his efforts to stage the crime scene, dispose of the bodies and evidence, and then effectively evade from justice for an extended period of time.
In such a case, his version should simply be discarded, except where corroborated by solid evidence.
There is simply no evidence to corroborate the idea that CC was killed in an accident for example. Indeed quite the opposite. Ditto there is no evidence RH was accidentally killed or in some kind of self defence - in my view. These are nothing more than bare assertions.
Indeed the whole defence seems to be 'why would GL do this" but that is not really a credible defence given we know he did indeed kill the victims and engage in elaborate staging.