The Golden Thread of our common law criminal justice system contains important principles that are basic and fundamental to being Canadian. These principles are The Presumption of Innocence, The Burden of Proof and Reasonable Doubt.
This small video illustrates in a real way the importance of defending against the erosion of The Golden Thread:
The Presumption of Innocence:
The presumption of innocence lies at the very heart of the criminal law and is protected expressly by s. 11(d) of the Charter and inferentially by the s. 7 right to life, liberty and security of the person. This presumption has enjoyed longstanding recognition at common law and has gained widespread acceptance as evidenced from its inclusion in major international human rights documents.
In light of these sources, the right to be presumed innocent until proven guilty requires, at a minimum, that: (1) an individual be proven guilty beyond a reasonable doubt; (2) the State must bear the burden of proof; and (3) criminal prosecutions must be carried out in accordance with lawful procedures and fairness.
A provision which requires an accused to disprove on a balance of probabilities the existence of a presumed fact, which is an important element of the offence in question, violates the presumption of innocence in s. 11(d). The fact that the standard required on rebuttal is only a balance of probabilities does not render a reverse onus clause constitutional.
Burden of Proof:
The obligation to produce evidence to prove facts necessary to establish a cause of action or a defence. It normally rests on the person who asserts a particular matter.
In the criminal context, the Burden of Proof lies with Her Majesty the Queen or the Crown prosecution.
The standard of proof beyond a reasonable doubt is inextricably intertwined with that principle fundamental to all criminal trials, the presumption of innocence;
Source: R v. Avetysan,  2 SCR 745, 2000 SCC 56 at par 10