Why not deism?

[chimp3]

No different. I would hope that the expert witnesses would support their argument with scientific data. I would hope the expert witness was not taken at their word just because they are considered an authority.

In the cases I've watched so far, the experts are pretty clear on what leads them to their conclusions. It's generally science or experience in a field. 

But in this case it seems you are accepting authoritative testimony as evidence. Perhaps with the stipulation that "authoritative" includes something like "science-based."

In the court room setting I would hope that "authoritative" is a synonym for "expert". So, that includes something like science based.  In the court setting their testimony is not evidence, they are presenting evidence. Ballistics, Pathology, etc. Regarding a religious claim authorities have a much higher hurdle. If someone claims they are an authority on exorcisms I could just as easily claim I am an authority on talking, flying frogs. They have to support their claim with the evidence for demon possession, not just anecdotes.