Jim, I agree that the idea that we should do a better job in describing, or at least articulating, how confident we are in our conclusions in a particular investigation. Believe me, I feel the pain that comes with the need to "get it right" when lives will be affected by my call. But I have a problem (all due respect to John, et al) with labeling a degree of certainty by either a percentage or a term like "To a reasonable degree of scientific certainty." What does that mean? It seems to mean that you are really, really sure that you got it right. And I'm sure that you think you did. But I am really, really, really sure that I am right. So, if you want me to use the words "scientific certainty", I will (because I know I'm right.) But now my scientific certainty is at odds with your scientific certainty ... so let's settle it like learned scholars. How sure of your call are you in terms of percentages? [You say that you are 98% certain that you are right.] Aha!!! See, I am 99.73% certain of my call and therefore: I am correct. Forgive the subtle allegory, but using really strong words doesn't provide any more support to the conclusion. (In the movie "Tommy Boy", the late Chris Farley's character says that he can put crap in a box and call it guaranteed, but all you've got is a guaranteed box of crap.)

Another problem arises when you have provided a rational and possible alternative cause (that you are scientifically certain of.) All the testing in the world may show that your scenario can or will result in a fire, but it doesn't prove that it started this fire. My scenario may be just as scientifically valid and empirically tested - but I have to articulate why I think this is the most probable series of events in this case! This will always be the dispute when opposing experts meet. Not so much that one of them has a really bizarre or far-fetched explanation - those are easy to refute - but that both have plausible causes.

I wish there was a better way to describe a level of certainty, but, as I've stated before, I fear that "Probable" is still the best we've got going. If you want to change the 921 definition of probable to 57% or better, 81% or more ... 90%, that's fine with me, but it is not an easily quantified concept and so you will merely have investigators who raise their level of certainty with no further proof offered. Very difficult issue to resolve finally and sound arguments exist pro and con.
(I love a good philosophical debate!)

Steve