A Facebook fan of Genealogy Tip of the Day asked whether beyond reasonable doubt is the level genealogists want to reach. Here's my short response:
Beyond reasonable doubt is usually too high a bar for genealogical researchers to cross. Preponderance of the evidence and reasonable suspicion are usually a little too low of a threshold--genealogists need to be a little more certain than that. The closest usual level suggested for genealogical proof is "clear and convincing" which would be a stronger case than a preponderance of the evidence but not as strong as beyond reasonable doubt.
In actuality, genealogists usually don't use these legal terms to describe genealogical proof. At its simplest, genealogical proof is searching all extant relevant records, extracting relevant information from those records, and organizing that information in a way that makes the researcher's conclusion clear. The organization and writing is the proof. The information obtained from records and used in the proof is the evidence.