 Before auditioning for "Australian Idol", Leith worked in Sydney as a chemist with Pharmalab utilising the Bachelor of Science (Honours) in Chemistry he obtained from University College, Dublin and postgraduate experience within the Metallosupramolecular Research Group in the Chemistry Department of Trinity College, Dublin.Only following determined coaxing by friends, Leith auditioned for the 4th series of Network Ten's Australian Idol along with some 25,000 other contestants.He was selected by the judges as one of the final 24 contestants, and was the first person voted into the competition's top 12 as the result of a nationwide viewer vote.