The New Zealand Racing Board is before a jury in the High Court in Wellington accused of defaming a gaming trust, the First Sovereign Trust and several people associated with it in a media release distributed by the board in November 2010.
The media release said that the NZ Racing Board denied involvement in poker machine fraud, which it said had been implied by a National Business Review article.
The plaintiffs' lawyer told the jury on Monday that his clients believe the media release suggested they had been complicit in such fraud and that they lacked integrity.
Each of the plaintiffs is seeking $200,000 in general damages and $50,000 in punitive damages.
The New Zealand Racing Board denies the accusations.
A jury of five men and seven women has been chosen to hear the case, which is expected to run for the rest of the week.