The presumption of innocence, sometimes referred to by the Latin expression Ei incumbit probatio qui dicit, non qui negat (the burden of proof lies with who declares, not who denies), is the principle that one is considered innocent until proven guilty. Application of this principle is a legal right of the accused in a criminal trial, recognised in many nations. The burden of proof is thus on the prosecution, which has to collect and present enough compelling evidence to convince the trier of fact, who is restrained and ordered by law to consider only actual evidence and testimony that is legally admissible, and in most cases lawfully obtained, that the accused is guilty beyond a reasonable doubt. If reasonable doubt remains, the accused is to be acquitted.



http://en.wikipedia.org/wiki/Presumption_of_innocence