THE defence in the trial of former Mandurah school principal Matthew Faulkner will come down to one single fact, according to his lawyer; he simply "didn't do it".
Mr Faulkner, 54, has pleaded not guilty to 11 child sex charges.
The first day of his trial got under way on Monday morning with a jury hearing opening statements from both the prosecution and the defence.
The State is alleging Mr Faulkner engaged in sexual conduct at his Halls Head home with a teenaged boy in 1997.
Also alleged is indecent abuse at a Thornlie primary school where Mr Faulkner taught during the early 1980s.
The charges include two counts of indecent dealing with a child under the age of 14, eight counts of sexually penetrating a child between 13-16 and one count of procuring a child aged between 13-16 to engage in sexual behaviour.
Monday morning saw the first testimony presented by one of the complainants.
Appearing via videolink, the man broke down as he detailed various incidents where Mr Faulkner is alleged to have fondled him and engaged in oral sex with him.
While maintaining his denial of any sexual offences, Mr Faulkner has admitted supplying alcohol, cigarettes and marijuana to underaged boys during the time of the alleged crimes.
He also admitted teenaged boys were at a party he hosted at his home around the same time a stripper was present.
The trial continues.
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