Evening all

I'm trying to help my in-laws, they have an Samsung GT-S7580, which is installed in a 'flip' case.  While it is in this case, it makes an audible noise, like it is waking up.  If you open the case and have a look, it is opened Google Now.

I went looking for an option like on an iPad to disable the cover lock - however I didnt have much luck in finding such a setting.

Any ideas on what this could be, or the presence of such a setting.

Thanks in advance.
David