Oscar: Justice was served

Oscar should have told the truth from the start. He has given the courts the run around. Manslaughter 5 years sounds about right for a man shooting in an uncontrollable rage. That's manslaughter by reason of temporary insanity. I think the sentence suits the above scenario. But why and who advised Oscar to come up with the highly improbable story of the intruder. He actually opened himself to the more serious crime "dolus eventualis"   Another judge could definitely have ruled in favour of the prosecution.