In A-Dec, Judge Bouck used these words:
"Letters rogatory are sometimes known as letters of request. They constitute a request from one judge to another asking for the examination of a witness by commission in the jurisdiction which is foreign to the requesting court."
In R v Buchanan, Justice Trussler adopted these words:
"... letters rogatory are defined as ... a commission from one judge to another requesting him to examine a witness. In the terminology of international law this expression is used as a synonym for what in our law are known as letters of request addressed to a foreign court.
"Letters rogatory are the medium, in effect, whereby one country, speaking through one of its courts, requests another country, acting through its own courts and by methods of court procedure peculiar thereto and entirely within the latter's control, to assist the administration of justice in the former country; such request being made, and being usually granted, by reason of the comity existing between nations in ordinary peaceful times."
Also known also as rogatory letters, letters of request or even commissions to collect evidence.
REFERENCES: