Watched one of the Portuguese documentaries that the McCanns tried to ban. The main thing that stuck out to me was that the extremely reliable sniffer dogs found traces of a dead body in the cupboard of their/her room and also in a car that they had hired. 
There was blood found in the boot of the car, a fair amount of it and it had appeared that it had been cleaned, and when I say cleaned I mean attempted to properly clean it, not 'the steaks have leaked a little bit of blood' and wiped clean.
So was it her blood then?
It's highly likely. Like I said there was clear attempts to make it look like there was no blood there at a forensic level, not just the naked eye. Thats not an extent you would go too to clear up some spillage off steaks in a rental car, and on your holiday. Would you go to such lengths to clean your rental car if you were on holiday?
You could argue that, if they were guilty, why would they want to continuously have the case in the media? Why wouldn't you want it to quiet down, after 6 years especially, and just carry on a private investigation into it. A variation on Munchausen's Syndrome?
I can't imagine a scenario personally, where they found their bairn deceased, and both decided in that split moment to lie about it for the rest of their lives.
Precisely that, because of their guilt. They could be deluded enough to think that if someone else is convicted or largely believed to have taken/killed Maddy then their guilt would no longer be with them because they are no longer the ones seen to have done wrong and in their eyes are proven to be innocent.
However you could also totally spin it and it could be because they don't feel guilt at all, in fact they don't feel anything. The are both white, both intellects, both middle class, both the typical 'people who would have thought could never do such a thing ', all traits of a Psychopath.If they are then they can see things from a purely logical point of view. If they had have accidentally over dosed Maddy on medicine in order to make her sleep or accidentally killed her another way then they could look at it from how it would make them look. They are people in financially rewarding jobs, highly respected skilled jobs, if they were have found to have been responsible for the death of their own daughter even under the terms of manslaughter then their career/lives/image would be ruined. Now take it back to having them having emotion but thinking logically, they would know that if they were found guilty for their daughters death they would no longer have custody of their remaining children.
Plenty of people are quick to say "I would never do that, if that was my child I could never/would never do that" forgetting that other people's logic can be so different and that other people can lack the simplest of emotions which make things for the average person impossible to do or bear thinking about.
