Any person of or over the age of 16 years who—

1. (a)

   has sexual intercourse with a child under the age of 16 years;

2. (b)

   is a member of the same household as that child; and

3. (c)

   is in a position of trust or authority in relation to that child,

shall be guilty of an offence, unless the accused proves that he or she—

1. (i)

   believed on reasonable grounds that the person with whom he or she had sexual intercourse was of or over the age of 16 years; or

2. (ii)

   did not consent to have sexual intercourse or to have sexual intercourse with that person; or

3. (iii)

   was married to that person, at the time when the sexual intercourse took place, by a marriage entered into outside Scotland and recognised as valid by Scots law.