The trial of two top aides to former Liberal premier Dalton McGuinty is hearing arguments about whether a key prosecution witness should be able to testify as an unbiased expert.
Defence lawyer Scott Hutchison told a Toronto court that former police officer Robert ``Bob'' Gagnon should be disqualified as a witness in the case.
Hutchison says Gagnon cannot be considered independent and impartial, since he was an intimate member of the team that investigated and prosecuted David Livingston and Laura Miller.
Both of them have pleaded not guilty to illegally destroying documents related to the Ontario government's cancellation of two gas plants ahead of the 2011 provincial election.