Blinding me with Science

I was recently raked over the coals by Katherine Ramsland for comparing dactyloscopy to phrenology and spectral evidence. In my own defense, I was not making a literal comparison, only citing examples from history where generally accepted practices were later found to be unreliable. This was in response to a phrase I thought I read in her article--that the underlying assumption of dactyloscopy, that no two persons have identical fingerprints, has never been proven, and as such, is an urban myth. Certainly the forensic study of dactyloscopy is scientific, and the points of comparison between two fingerprints can be trusted in a court of law. My point was somehow lost in this exchange--which was, that jurors mostly do not have the wherewithal to independently verify the assertions of scientists on the stand, that they must trust those conclusions on faith. Faith that the scientist is telling the truth and that his or her method is sound. I don't think that prosecutors can as jurors to take scientific evidence on faith. They MUST educate jurors in the science, or risk them disregarding the evidence as irrelevant.

It's like the legal term "beyond a reasonable doubt." What exactly does that mean? And how does it differ from "a preponderance of the evidence" or "clear and convincing evidence?"

I'm speaking here only as a layperson. Katherine Ramsland, with her scientific/forensic background would never be picked to be on a jury. I have a jury summons laying on my desk as I write this. These are questions that matter.