I think it has already been demonstrated that the metadata is rather easily altered.
The key will be the watch in the photos, and Nifong is almost guaranteed to say the watch was set wrong on purpose, going by the other odd things he has said.
http://www.slate.com/id/2140303/
but not if you have the device. they have the device.
I think it's going to be difficult to argue that the images have been altered. It's true that it can be done, but there are a lot of problems. suppose the camera keeps a record of activity, or suppose the images were emailed in a timely fashion.
Photographs are generally accompanied by testiomony, and the Duke students have a number of unindicted people to testify as to the timeline. You can't just alter one number in a file and expect to get a way with it. You have to change the whole sequence of images and make it conform to reality.
But the "explainer" does not say whether changing the metadata leaves a trace or trail of when the data was changed. Still he was definitive enough to make me want to see a definitive statement of what can and cannot be done with this type of image file.
Of course the strong plus here is that the time frame is already pretty well defined by independent observers - the neighbor, taxi driver, ATM camera. Still with the potential for a rogue DA, the more evidence you have the better.