Appearing in the Royal Court on Friday, Myles Robert Killan entered a guilty plea to the offence committed 26 June this year on a basis which was accepted by the Crown.
The court remanded Killan on conditional bail until 14 January, when he will be sentenced by the Inferior Number.
Defence lawyer Advocate David Steenson said that his client had recently been diagnosed with autism and attention deficit disorder, which may have been contributory factors in the assault, and the court ordered psychiatric and social enquiry reports to be compiled.
Lieutenant-Bailiff Anthony Olsen was sitting with Jurats Charles Blampied and Robert Christensen.