Former prison inmate Josette Bickle has been convicted by a jury of drug possession and trafficking at the prisons between 2006 and 2008.
The jury returned an 8-1 verdict after some three hours of deliberation.
The trial started on Monday, with the court hearing how Bickle lived 'like a queen' and had practically free rein at the prisons. Fellow inmates claimed they were treated as her 'slaves' and warders were afraid of her.
The court was also told that Bickle amassed a quantity of items as payment for drugs, including four televisions sets and a sound surround system. Money given to the prisoners for their work was also diverted to her.
Sentence is expected tomorrow.