The presumption of innocence is a fundamental principle in the criminal law of the United States, relieving criminal defendants of the burden of proving their own innocence. Criminal defendants in the United States are innocent any crime until proven guilty, placing the burden of proving guilt upon the prosecution. The government is given the responsibility of producing enough evidence and arguments to prove the guilt of criminal defendants beyond a reasonable doubt. No matter what indictment or formal charges are brought against the defendant, and no matter what the personal feelings of those involved may be, if government prosecution cannot decisively demonstrate the defendant's guilt in trial then that person is legally "not guilty" and free to go.
It has been ruled by the Supreme Court that a judge must issue special instructions to the jury on the principle of the presumption of innocence, under some circumstances. Special instructions on the presumption of innocence may be required in cases where the jury may be tempted to convict the defendant based on extraneous considerations rather than the weight of the prosecution's evidence in the case.
The release of the defendant from jail before his or her trial is favored under the principle of the presumption of innocence, provided that bail is met. The Eighth Amendment to the Constitution also supports this stance, by prohibiting courts from setting excessive bails. However, in cases where the defendant is being charged with a very serious crime and is considered likely to pose a danger to the public, it is widely accepted that he may be held without bail.
In a very important sense, the presumption of innocence is a symbol. No one would ever be brought to trial unless there was reasonable possibility that he or she did in fact commit the crime in question. If John is accused of burglarizing Allen's shop and brought to court for the supposed crime, John's claims of his own innocence are fully accepted - until security camera footage that clearly depicts John in the act is shown to the court. After that moment, it is unreasonable to assume that John is anything other than guilty (although his attorney is free to present a number of excuses or justifications in his client's defense.) Once enough evidence has been presented to give the court probable cause to believe the defendant is guilty of the crime, he is no longer treated as if he were innocent, and may be incarcerated with the full sanction of the law.
The presumption of innocence principle, while it may sometimes hold no more than a symbolic meaning, is an essential element of the United States criminal law system. The inquisitorial counterpart to this principle, the presumption of guilt, has been rejected by the people of this nation as antithetical to the spirit of a free society. The presumption of innocence remains, therefor, one of the pillars upon which our freedom rests.