Definition - What does Proof mean?
The legal definition of proof refers to some sort of fact that is proven due to evidence put forth during a law suit or trial. However, there are many things in a trial setting that cannot be conclusively proven. So, legal proof is based on anything that can make a jury or judge more or less likely to believe the allegations.
Justipedia explains Proof
Whether something is proof, and how strong the credibility of the proof actually contains, is largely contingent upon the burden of proof that is required in order to find guilt or liability in a legal case. For example the burden of proof is much higher in a criminal case then it is in a civil case. So, while something might be seen as persuasive proof in a civil case might not be seen as persuasive proof in a criminal case.