presumption of innocence
The presumption of innocence is a simple promise the law makes to everyone accused of a crime: until the case against you is actually proven, you are treated as innocent. Picture a courtroom scale that does not start out balanced — it starts tipped in your favor, and the prosecution has to pile on enough solid evidence to tip it the other way.
This matters because it decides who has to do the work. You never have to prove you didn't do it; the state has to prove you did, and prove it convincingly — in serious criminal cases, beyond a reasonable doubt. If they fall short, you walk free, even if some doubt lingers. Better that than punishing people on suspicion alone.
A common mix-up: a 'not guilty' verdict does not mean the court declared you innocent or believed your story. It means the state failed to prove its case to the required standard. Innocence was the starting point all along — the trial was only ever a test of the prosecution's proof, not of your goodness.
The principle is often summed up as 'innocent until proven guilty,' and the Latin maxim ei incumbit probatio qui dicit — 'the burden of proof lies on the one who asserts' — traces it back to Roman law. It is enshrined in the Universal Declaration of Human Rights (Article 11).