I happen to think it was VT. I agree that it is not vitally important for the case now as he has been convicted of murder. However, I think it may shed light on a part of what happened that night if it is him. My theory is that he saw Jo in Waitrose and as she was on her own and so was he, he decided to act upon his dark compulsions and made sure to follow her or to get back first and wait for her to arrive home. Just my opinion. I don't understand why the prosecution did not use it to add to the possibility of intent, but maybe they didn't have any clear enough images they could use.