A DRIVER who acted as a substitute candidate to secure driving test passes for clients was jailed for six months yesterday. Tam Yuet-ming, 26, pleaded guilty in South Kowloon Court before Magistrate Michael Hill to conspiracy to defraud. The court heard that Tam and another person operated a substitute candidate service charging clients up to $20,000, and that Tam obtained two driving licences between November 1 and December 31 last year.