A formal written request made by one judicial body to another court in a different, independent jurisdiction that a witness who resides in that jurisdiction be examined through the use of interrogatories accompanying the request.
A device used ininternational lawby which the courts of one country ask the courts of another to utilize their procedure to assist the country making the request in the administration of justice within its borders.
The use of letters rogatory can be traced to early American legal history when they facilitated cooperation between the courts of the several states of the Union. Their continued use is based primarily upon the comity (courtesy and respect) of courts toward each other. Rule 28 of the Federal Rules of civil procedure provides for letters rogatory to be used in federal courts to obtain the testimony of a witness who resides in a foreign country through a number of different discovery devices. The Convention on the Taking of Evidence Abroad in Civil or Commercial Matters (28 U.S.C.A. § 1781 ) sets out the procedures to be followed in the use of letters rogatory by the countries who are parties to the treaty.
Letters rogatory can be sent to a court in a sister state or to a court or judge in a foreign country. Granting the request, again, is a matter of comity between courts.