The Sydney University student was dancing with friends and kissing a man at the St John's College end-of-year formal.

The next thing the woman remembered was being in a leafy area with overhanging trees on the grounds of the college with the man, Jean Claude Perrottet on top of her, the NSW District Court heard.

Jean Claude Louis Perrottet (left) is charged with three counts of having sexual intercourse with a woman without her consent. Credit:Kate Geraghty

Mr Perrottet, 20, the younger brother of NSW Treasurer Dominic Perrottet, is charged with three counts of having sexual intercourse with the 19-year-old woman without her consent in the early hours of October 18, 2015. Mr Perrottet has pleaded not guilty.

NSW District Court judge Stephen Norrish informed the jury panel of Mr Perrottet's politician brother before 12 members were selected.