I keep hearing “burden of proof” and “beyond a reasonable doubt” but what do these terms     mean?
Burden of proof can define the duty placed upon a party to prove or disprove a disputed fact, or it can define which party bears this burden. In criminal cases, the burden of proof is placed on the prosecution, who must demonstrate that the defendant is guilty before a jury may convict him or her. But in some jurisdictions, the defendant has the burden of establishing the existence of certain facts that give rise to a defense, such as the insanity plea. In civil cases, the plaintiff is normally charged with the burden of proof, but the defendant can be required to establish certain defenses.

Commonly in Minnesota courts “beyond a reasonable doubt” is defined as, “such proof as ordinarily prudent men and women would act upon in their most important affairs. A reasonable doubt is doubt based on reason and common sense. It does not mean fanciful or capricious doubt, nor does it mean beyond possibility of all doubt.”