I have no way of knowing what was in their minds at the time. The may have been telling purposeful lies, they may have been accidentally mistaken.
As with Amaral's thesis, I am willing to give both camps the benefit of the doubt- I have no evidence that either party was lying, but I can see that there are inconsistencies in what they have stated.
Lying is a very strong word and should only be used to mean what it does mean- telling an untruth with the intention of misleading.
http://www.mccannfiles.com/id107.htmlMadeleine Father Portugal Return
Q: Do you plan to cooperate with the Portuguese authorities?
GM: Of course.
Q: Are you going... are you going to meet with, errr... Portuguese authorities...
GM: Uhhh, we haven't...
Q: ... this time?
GM:The purpose of this visit was to, errr... really look at what can still be done in the search, we want to be, you know, looking positively, not backwards - looking forwards. 'Cause, you know, we want to find our daughter. It's pretty simple really.
As we know from Madeleine Gerry McCann went to Portugal specifically to plot the libel claim and gagging order with Duarte. In perhaps the most prolonged and widespread example of his gratuitous lying he gave interview after interview stating that he was there for other reasons.