I agree with what you are saying and that is my point. Your wording, “To a reasonable degree of scientific certainty, I think this is the probable cause of the fire” is a very clear description of you findings. The way you go about explaining other hypothesis is right in line with my thinking. You are keeping plain and simple to where any person can understand the points you are trying to make. I understand about how error rate was used in Daubert and agree with you on that subject. My problem is the wording used in 921 for defining “Probable”.

I am not talking about a margin of error but only the fact that for my conclusion to have the level of certainty of being correct it needs to be more probable than not or be greater than 50%. I believe as it is defined in 921 that is a low thresh hold for believing something is correct. I would rather see the document give guidance to the investigator with the wording “To a reasonable degree of scientific certainty” than the possible and probable. I would not mine seeing probable remain with a better definition.