Rules of evidence are developed to assist the judge in his/her attempt to determine the true version of events, and therefore make a fair and responsible ruling. However, there are certain types of communications that are so important that they must be protected, even if this means that the truth may be obscured. These communications are referred to as being “privileged”.
There are several types of relationships that give rise to privilege. One would be the lawyer-client relationship. Any conversation between a client and their lawyer cannot be repeated by the lawyer without express permission from the client. The purpose of this rule is to enable people to be completely honest with their lawyer in an attempt to protect their freedom. The lawyer could not defend the client to the best of her ability without all of the facts. But the client may not want to be completely honest about their case if they knew the lawyer could tell other people.
There are exceptions to this rule. For example, if you consult a lawyer because you want to kill someone and you are looking for advice on how you can do this and escape punishment, these communications will not be privileged; in fact, that lawyer likely has an obligation to report you. Another example would be instances of suspected child abuse. As in the medical profession, if a lawyer believes that a child is in an abusive situation they are obligated to report this to the authorities even if they have learned about the abuse through privileged communications with their client.
A second type of privilege would be marital privilege. A spouse cannot be forced to testify against another spouse with regard to the communications made between them while married. The purpose of this rule is to help protect the sanctity of marriage. Obviously forcing a person to testify against their spouse would cause irreparable damage to their relationship. It would also put a spouse in a position where they would have to choose between the possibility of perjury charges or betraying their spouse. It is interesting to note that in Canada a spouse is not forbidden from testifying, but allowed to choose not to. This privilege likely does not apply after divorce.
A third type of privilege would be the right of privilege against self-incrimination. Canadian human rights legislation protects this right. This type of privilege means that a person who is accused of a crime cannot be forced to testify in their own defense. One reason often cited for this would be the fact that the government has so many resources available to them to assist them in convicting an accused person. The accused person may only have the help of an over-worked, under-paid lawyer to assist in their defense. Given this imbalance, some would argue that the government has enough help convicting without forcing the accused to testify.