University of Miami law school professor Tamara Lave:

Beyond a reasonable doubt should be contrasted with presumption of the evidence, which is the burden of the moving party in a civil action. Presumption of the evidence means that the moving party must prove his or her case by a 51% burden. They just need to tip the scales slightly to prevail.

Orlando defense attorney Lyle Mazin:

It is the standard of proof required in all criminal cases in order for a jury to reach a verdict of guilty. The best way to understand what beyond a reasonable doubt is, is to understand what it is not. Beyond a reasonable doubt is not the same standard of proof required by its sister standard by 'preponderance of the evidence' which is the standard of proof used in many civil trials. Read more here.