Results of health tests on three prison officers who had the contents of a mop bucket thrown over them by a laughing inmate came back clear, Coleraine Magistrates Court heard on Monday.
Dylan Smyth, 26, with an address given as the Galgorm Road in Ballymena, soaked the officers during an incident in Magilligan Prison before he ran off and locked himself in a cell.
A prison officer slipped and suffered a back injury during the incident, a prosecutor said.
The defendant appeared at the court via video link from Magilligan jail and admitted three charges of assault.
A defence solicitor said it was an "unpleasant offence".
He said there had been "no repetition".
District Judge Peter King said the prison officers had been going about their lawful duties.
He said: "Nobody knew what was inside the material that came over them".
The judge said such offences had to be taken seriously but thankfully there were no health consequences for the prison staff.
Smyth was given a three months jail sentence for the offence.
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