Pitcher, 46, of Norman Way in Wootton, now faces a prison sentence after jurors at the Isle of Wight Crown Court found him guilty this afternoon (Monday).
The historical offences occurred between 1990 and 1992, more than 30 years ago, when Pitcher was a child.
The jury returned a guilty verdict after hearing arguments from both the prosecution and the defence for six days, including a statement from the victim in which she claimed Pitcher penetrated her twice and stole her virginity.
The victim did not understand what had happened, according to the court, and it was only after having sex education classes at school that she realised it was wrong. Until recently, the victim claimed she blamed herself for the incidents, but only through therapy and counselling did she realise this was not the case.
Recorder Richard Onslow summarised the case and sent the jury out early this morning, with the verdict being returned in just 5 hours.
The Wootton councillor has always denied the charges.
The case has been adjourned until April 12th for sentencing at the Isle of Wight Crown Court.