They made a big point about the door. It's clearly written in her diary. Gerry talked about it being half open when he checked.
Pages 891 to 903 Gerald McCann 10 May 2007
"----- He followed the normal route up to the rear door, which being open he only had to move [slide] it, that being the way in which he entered [was entering] the lounge, he noted that the children's bedroom door was not ajar as he had left it but half-way open, which he thought strange, having then put together the thought of MADELEINE having got up to go to sleep in his bedroom so as to avoid the noise produced [created] by her siblings. In this way he entered the children's bedroom and established visual contact with each of them, checking and is certain of this, that the three were sleeping deeply. He left the children's bedroom returning to place the door how he had already previously described, [then] going to the bathroom. Everything else was normal, the blinds, curtains and windows closed, very dark, there only being the light that came from the lounge."