Posted Wednesday, October 10, 2012 --- 11:33 a.m.

MADISON, Wis. (AP) -- A state appeals court says a prisoner who threatened to kill two Sheboygan County judges was properly convicted.

Prosecutors say Martonez Wallace had a fellow inmate at Waupun Correctional Institution mail threats to Judge Timothy Van Akkeren and Judge Gary Langhaff. A jury found Wallace guilty of two counts of threatening a judge in 2010.

Wallace argued his fellow inmate, Jessie Williams, wasn't believable. He contended Williams told investigators he picked the judges' names at random out of frustration against the judiciary, later changed his story to say Wallace offered to pay him and reverted to his original story at Wallace's trial.

The 2nd District Court of Appeals ruled Wednesday it's up to a jury to decide a witness' credibility.

Wallace's attorney, Kyle Conway, could not be reached for comment.

Copyright 2012. The Associated Press.