According to Fiona Payne Kate said the patio door was left unlocked so that Madeleine could get out if she needed to.
http://www.mccannpjfiles.co.uk/PJ/FIONA-PAYNE-ROGATORY.htm
Text from FP rogatory: "Reply
'She did, she brought it up and that she, I mean, this is awful in retrospect as well, she asked what my opinion was on, erm, tut, on whether they were okay leaving the,
the doors unlocked, because she was saying 'Is it better that if Madeleine wakes up she can get out and find us or', erm, 'or locking it and, you know, finding that we're not there and the door's locked if she woke up', because Madeleine had woken up, what I thought was the night before. Erm, tut, and it was in that context really, just asking, you know, what I thought. So it was obviously something that was on her mind a bit, huh'.
01.15.57
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'So she asked you what your thoughts were regarding locking''
Reply
'Yeah'.
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'Did she say whether she had locked or''
Reply
'No, that was the point, I think they said they'd left it, well she'd said she'd left it unlocked'.
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'Left the patio''
Reply
'And she felt a bit nervous about it but Gerry, Gerry had sort of said 'Oh it will be fine', you know. But she was obviously, because it wasn't something she was quite easy with, that's the way it came across, you know, but, but Gerry said, you know, 'It'll be fine. It'll be fine'. Because I don't imagine she would have said anything otherwise if it hadn't been on her mind. And the fact was she, she, you know, commented on it being really strange that, that Madeleine had said this about waking up and them not being there and she'd mentioned that in the context of that conversation'."
In there are the words
the doors unlocked which clearly means both doors were unlocked at least from the inside. Solely for the purpose of allowing Madeleine to get out if she woke up. So why would Gerry say his daughter never went outside? OK it was he considered the evidence of an abduction overwhelming.