A convicted murder threw "excrement" over a prison officer in HMP Frankland as his appeal against his conviction was taking too long.
Robert Firkins was serving a life sentence at the category A prison in Brasside, County Durham, after being convicted of murder in January 2006.
The 49-year-old, who has "protested his innocence" ever since, has lodged an appeal against his conviction, and in 2020 the Criminal Cases Review Commission (CCRC) sent the case to the Court of Appeal.
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But Firkins became "annoyed" at the length of time the process was taking, and on June 5, last year, he vented his frustration by throwing "faecal matter" over a prison officer.
Firkins appeared at Durham Crown Court on Wednesday, via link from HMP Full Sutton, to be sentenced for administering a noxious substance with intent to injure, aggrieve or annoy.
He pleaded guilty to the charge at the hearing.
Shaun Dryden, prosecuting, said the HMP Frankland prison officer was "walking down the landing" on the afternoon of June 5 when he was approached by Firkins.
CCTV showed Firkins removing a "protein shaker" from his shorts, before "throwing the contents towards" the officer.
Mr Dryden said the protein container contained "faecal matter", and it hit the officer in the face as Firkins walked away.
He was then "restrained" and the officer went to hospital to undergo tests and have bloods taken.
In a victim statement, the officer said the incident left him "humiliated and embarrassed", and feared of infection.
The court was told that Firkins had a previous conviction for murder and is serving a life sentence.
In mitigation, Farrhat Arshad said Firkins had lodged an appeal against his conviction, and in July 2020 it was sent to the Court of Appeal.
However, since then, "nothing had happened" and appeal papers were still awaiting to be served so "it can get underway".
She said that Firkins has "protested his innocence" ever since his conviction and that he had become "stressed" at "having waited a very long time for his appeal to be heard".
Ms Arshad said that the "history of the appeal explains why he behaved the way he did".
She added that Firkins was "sorry" and "accepted he was badly behaved" and that it was "out of character".
Sentencing him, Judge Ray Singh, said Firkins had become "annoyed" that his appeal had not yet been granted and so committed the offence.
He said there was "absolutely no justification for what you did" and said Firkins "must have planned" it.
Firkins was given a two year prison sentence, which will be served consecutively to his life sentence.
