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.