What is solicitor and client privilege and what is its purpose?

33 The rationale behind solicitor and client privilege is the safeguard of a client’s ability to fully disclose to his or her lawyer information regarding the case with the assurance that these communications are made in confidence. Put another way, the purpose behind this form of privilege is: …to ensure that a client is free to tell his or her lawyer anything and everything that is pertinent to the case, without any fear that this information may subsequently be divulged and used against them. Without this freedom, there is the possibility that the lawyer may not have the benefit of all the relevant information, and may not be able to do his or her job effectively. And that possibility must be avoided as contrary to the interests of justice. (Stevens v. Canada (Prime Minister), supra, para 12)