Simple answer is it cannot. As already pointed out, these proceedings are about seeking compensation for the damage alleged to have been done to the McCann family when Gonçalo Amaral published his book and DVD. The witnesses brought to court by the McCann lawyers all gave evidence on this basis.
The
libel trial is about assessing damage, both to the reputations of the McCanns and the search for Madeleine caused by a book and a video that both assert (contrary to truth) that Madeleine was established as dead by the shelved enquiry, that the McCanns know she is dead and covered up the fact of her death and that the McCanns launched a fraudulent "appeal" in their (dead) daughter's name.
I assume most would agree that Isabel Duarte knows a thing or two more about Portuguese law than anyone here, and she believes the McCanns have a very good chance of succeeding.
Damages sought
are high by the standard that is usual in Portugal, I admit that.
But is there a (Portuguese) precedent for a book and a video published in several countries of one continent that peddles such falsehood on such a scale?
I bet there isn't.