I've not missed any point.
He's shot his girlfriend - fact. He's admitted to it - fact. He's claiming it was an accident, with a feeble story backing his claim. His story lacks credibility, as it's non-sensical for a whole host of reasons & anyone with an ounce of common sense would doubt it's validity, so therefore no-one is being 'ridiculous' for having an opinion as to his guilt, given the facts that are currently in the public domain. For him to excuse this murder as an accident, the reality is that it's him who needs to convince the Judge that his version of events is the truth, the proof is already there, she's dead, it was his gun, his house & he pulled the trigger.