White supremacist Philip Arps is being accused of sending letters of a violent nature from his jail cell.
Arps was jailed in June for distributing the live-streamed video of the March 15 mosque attacks in Christchurch.
The letters were raised in the Christchurch High Court where Arps was appealing his 21-month sentence.
It comes as the Corrections Department rushes to put more checks in place for letters written by prisoners with extremist views after it was revealed the accused mosque gunman sent two letters from jail that should have been blocked.
Eleisha Foon filed this report.