The letter relates to the bail hearing for one of two men accused of plotting to kill the prime minister.
It was sent to the chief executive of Courts Administration and copied to other members of the judicary.
Last week Prime Minister Tuila'epa Sa'ilele Malielegaoi said Justice Tafaoimalo Leilani Tuala-Warren leaked the letter's contents in court.
But defence lawyer Unasa Iuni Sapolu said its author and content only surfaced when requested by the prosecution, who were acting on behalf of the prime minister.
