Means, motive and opportunity are considered necessary for a criminal court case, but not sufficient. That requires evidence, (i.e. proof), to pass the ‘beyond all reasonable doubt’ test.
I have read of 4 categories of theories for Madeleine’s disappearance. If you can think of a different category, please leave a comment, as that would deserve consideration.
Madeleine got out of the flat on her own and then somehow disappeared.
It was a burglary that went wrong.
It was a planned abduction.
One or both parents of Madeleine are involved in covering up a crime in flat 5A, whether that involves death, and whether that death was accidental or not.
There are other theories floating about on the Internet that seem to not fit these categories at first glance, but what happens on closer inspection?
A burglary that turned into an abduction, whether or not Madeleine was harmed inside the apartment, is still a burglary that went wrong. The aim was burglary, not abduction, otherwise it would be a planned abduction.
Could Matthew Oldfield have been involved? If so, that would fall into either a planned abduction, or one or or both of the McCanns covering up. For the avoidance of doubt, I am not suggesting that Matthew Oldfield was involved, merely that this is a hypothesis that has to be evaluated.
Could it be much wider? I have read the hypothesis that the document signing Madeleine out of the afternoon crèche is a forgery, which certainly goes much wider. It still fits category 4, that one or actually both parents would have to be involved in a cover-up.
Could it be simpler? Perhaps the trio of children was too much for Kate, so around 10pm on 3rd May she passed Madeleine through the apartment window to a childless, grateful couple outside, and has regretted it ever since. For the avoidance of doubt, I am not saying this is what happened, merely that is has to be put to the test of means, motive, opportunity and evidence. This falls into category 4, covering up a crime in flat 5A. I am not aware of any law that makes it a crime to give your child away, however telling the police that it was an abduction would be a crime in itself, therefore it fits into the covering up a crime category.
If you have read any other theories, apart from aliens, comments and links are welcome.