A prisoner serving more than five years for a slash attack was found with a blade between his buttocks in HMP Perth.
John McCormack, 35, was found with a sharpened piece of plastic while being moved into segregation in October 2019.
Dundee Sheriff Court heard how McCormack’s life had been threatened by fellow inmates.
Fiscal depute Stewart Duncan said: “It was revealed to be a piece of plastic, sharpened to the handle, covered in tape.”
McCormack, a prisoner of HMP Addiewell, admitted possessing the weapon on October 15 2019.
Sheriff Lorna Drummond deferred sentence until July and released him on bail to an address in Glasgow.