Lawyers for Kate McCann have applied to the court in Lisbon for her to testify in the case of Goncarlo Amaral. Meanwhile, a decision is awaited on whether Madeleine's father, Glasgow-born Gerry McCann, can go into the witness box.
The couple are suing Mr Amaral, his publisher and documentary makers over claims made in a book, The Truth of the Lie, and a tie-in TV programme about Madeleine's disappearance from a holiday complex in May 2007.
A spokesman for the McCanns confirmed that lawyer Isabel Duarte lodged an application last week for Mrs McCann to also give evidence.
If the judge grants the applications, the couple are likely to give evidence at the end of the trial next month.
Mr Amaral is also awaiting a decision on his application to give evidence. Gerry's sister Trish Cameron claimed in court the family's pain over Madeleine's disappearance in 2007 was "multiplied 100 times" by the book.