In criminal law, there are several legal devises designed to protect the accused, one of which is the presumption of innocence, or the traditional rule that all suspects are treated as innocent until proven guilty. Among other ends, the presumption of innocence embodies society's commitment to the notion that, until the matter is settled in the court of law, an accused is just as entitled to the rights afforded by the law to legal persons as is his accuser. In this sense, the presumption of innocence has several consequences.
In forcing jurors and others members of the court to suspend their judgment until all the evidence have been heard and all arguments have been made, the presumption of innocence ensures that all criminal trials are taken seriously. Furthermore, as soon as a person is cast the role of the accused, he is put in a situation of a suspicious nature. Thus, it may be unavoidable that some jurors will enter his trial with some bias as to his innocence, and that some jurors will engage in estimating his probable guilt during the course of the trial.
For these circumstances, the presumption of innocence is a reminder to all members of the court that this is not how a criminal procedure ought to be. Even though its value to the legal process as introduced seems to be a very normative one, the presumption of innocence is also of great practical importance in structuring the procedure of a trial – more specifically, in allocating the burden of proof. It is a general rule in criminal law that, while the accused is presumed to be innocent, the prosecution bears the legal burden of proving guilt.
In this sense, the presumption of innocence expresses the incidence of the prosecution's burden of proof, his obligation to establish his case, the defendant's guilt, beyond a reasonable doubt. To say that an accused is presumed to be innocent is to effectively say that the prosecution must prove his guilt. It is important to note that, while the term presumption can refer to a "conclusion that may or must be drawn if another fact is proved,"1 the presumption of innocence has no factual effect; it is not a separate piece of evidence, an item itself that must be put to the jury2.
To treat the presumption of innocence in such a way is to propose that it states some intrinsically likely proposition, which it certainly does not. Rather, the only tangible effect of the presumption of innocence is the allocation of the burden of proof. Before we explore how the force of the presumption of innocence is delivered through the allocation of proof, however, it is helpful to look at an instance where the court refuses to apply a common law presumption to cast a legal burden of proof on the accused.
According to Cross and Tapper, there are two senses of burden, the burden of proving facts or the prosecution's legal burden, and the burden of adducing evidence or evidential burden. Woolmington v DPP demonstrates well the relationship between legal and evidential burden, or rather the court's insistence on the distinction between them, using the terminology of presumption.
In rejecting the trial judge's direction to the jury that killing is presumed to be murder unless proven otherwise and that it is the defendant's burden to prove his claim of self-defense, provocation, or accident, and in asserting that except for insanity and statutory defense, "there was no burden laid on the prisoner to prove his innocence and that it was sufficient for him to raise a doubt as to his guilt," the House of Lords in Woolmington rejects the old notion that the presumption of intention applies until it is proven otherwise, and moreover, specifies where the burden of proof lies.
But even though Woolmington rejects the application of the presumption of intention for the purpose of allocating burden, or more specifically, to cast a legal burden on the accused, it does this in the service of the presumption of innocence. In this sense, we can see how the effect of the presumption of innocence is the allocation of proof.