A secondary school teacher who helped the Metropolitan Police grade indecent images of children was caught on film as he abused a sleeping six year-old boy.
Special sergeant Craig Keane, 28, was captured on a camera hidden behind a curtain by frightened child as he molested the boy on 2 October last year.
Keane, a design teacher at The Sandon School, in Chelmsford, Essex, now faces jail after pleading guilty to nine counts of sexual assault on a child under the age of 13.
He has been suspended from both his roles as a teacher and special constable.
The Sandon School has informed parents the abuse does not relate to one of their pupils.
Heather Oliver, defending said: ‘He is a man of previous good character and even of positive character.’
Judge Alastair Hammerton said: ‘Although I have extended your bail I’m not giving an indication as to which way I or another judge will sentence you in March.’
Keane will be sentenced at Snaresbrook Crown Court on March 20.
Prosecutor Jeremy Hayes said the victim was asleep while the assault occurred but another child in the same room hid a camera behind the curtain to capture the abuse after becoming concerned about what was happening.
Keane, from Wickford, Essex, admitted nine counts of sexual assault on a child under 13.