Ivor Callely's case against the Seanad Committee investigating his expenses claims is due to be heard at the High Court today.
The senator is currently suspended after the committee found he had misrepresented his place of residence to claim €80,000.
The former Fianna Fáil Senator is looking for damages and he wants the findings of the Seanad Committee that investigated his expenses claims declared null and void.
At an earlier hearing, Mr Callely's lawyers said that he had been wrongly portrayed as a rogue and a pariah who had ripped off the State.
They will argue he was entitled to put down his house in West Cork as his "normal place of residence" for his expenses claims under the established guidelines.
Mr Justice Iarfhlaith O'Neill is due to hear the case over the course of this week.