Gerry McCann wants to testify in the case against Goncalo Amaral, who published a book about Madeleine's disappearance in May 2007.
The McCanns say the former detective's claims in the book The Truth Of The Lie, including suggestions that they hid their daughter's body after she died in an accident and then faked her abduction, damaged the hunt for Madeleine and exacerbated their anguish.
If successful in the case the family stands to gain around £1 million in damages.
Mr McCann was left frustrated after flying to Portugal last week, when proceedings were adjourned because one of Mr Amaral's lawyers could not be present.
Arriving at the Palace of Justice in Lisbon this morning, Mr McCann said he was not sure what would happen "after last week".
"We are here to listen to the judge and hopefully be heard," he told reporters.
He travelled to the Portuguese capital with his sister Trish Cameron, who gave evidence today, and his wife Kate McCann's mother Susan Healy, who is also expected to appear as a witness.
Mrs Cameron said the publication of his book in 2008 and a TV documentary based on it the following year caused the family to be "vilified" and "demonised".
And she said Madeleine's twin siblings Sean and Amelie, now eight, told their parents that comments were made by fellow pupils at their school.
She told the court: "My brother and sister-in-law live in purgatory because they have no end and they are looking for the truth.
"They would like an end but there is no end because they don't know what's happened."
Mrs Cameron, whose voice cracked as she described the effect on her family by the publication of the book, added: "They were vilified in this book so their distress was multiplied 100 times.
"This pain was felt by all of their family because we still have a missing child and we knew that what is in there is not true."
Mrs McCann attended the court last month on the first day of the case, telling reporters she was in Portugal to "stop the damage" she believes is being caused to the search for her daughter.
The court has heard how she had suicidal thoughts after Mr Amaral claimed she had covered up her daughter's death.
Psychologist Alan Pike said that after the publication of the former police chief's book in July 2008, Mrs McCann "thought about not being around any more".
Madeleine, who was nearly four, disappeared from her family's holiday apartment in Praia da Luz in the Algarve on May 3 2007 as her parents dined at a nearby restaurant with friends.
Mr Amaral, who initially led the inquiry into Madeleine's disappearance, was removed from the case in October 2007 after criticising UK police.
British detectives launched a fresh investigation into the youngster's disappearance in July this year and believe she could still be alive.
The Portuguese investigation into Madeleine's disappearance is officially closed.
The case, in which Mr Amaral denies defamation, is expected to finish hearing evidence in November.