Let’s see if I can answer your question. The percentage idea falls in well with the level of proof needed in legal proceedings. It is something that has been accepted and people can identify with it. Most people have been brought up being told that in criminal cases the burden of proof is beyond a reasonable doubt and in civil cases it is a preponderance of the evidence. People relate the civil proof as to being slightly above 50% to reach a preponderance of the evidence. Because so much of fire investigation interacts with the legal system it was easy to adopt this thinking. Problem is one has been adopted to cover both civil and criminal. We do not have a degree of certainty for criminal that is higher that that for civil. As of now, we are told that “probable”, which is being defined as being higher than 50% and a preponderance of the evidence, is sufficient to establish the cause for a fire for both.

I agree that “probable” is greater than 50%, but my question is how much above the 50% level is acceptable. Using the term flip of a coin was a little flip it on my part and I could have been better said. The point I was trying to make is that the difference between two hypotheses may only be two one hundreds of one percent and to choose one over the other may be nothing more than something as simple as flipping a coin.

There are those individuals that will disagree with what I am saying and say the level of proof is decided, not in the field, but in the court room. I can agree with that if the correct questions are asked of the expert so that the trier of fact will have all the information needed to completely evaluate all the facts. What if the question is never asked of the expert as to the level of certainty of his or her conclusion, or what percentage do they assign to their level of certainty of the conclusion. The expert is saying to the judge or jury this is the cause of the fire, not of the hypotheses developed I choose this one over the others and give it a 51% chance of being correct. If the expert did this he or she would still be within the guidelines of 921 for determining the cause, but how do you think the trier of fact would accept this information?

I am not saying my ideas on this subject are right or wrong, it is just something I would like people to think about when and if they are making a call as to the cause of a fire. If they were the person this determination could affect, what level of certainty would they be willing to accept? I have seen people whose lives have been negatively been affected by these type of determination and I believe every time one is made it reflects poorly on our profession. I know we can do better, and would like to see more effort to the profession going in that direction.