I think it was premeditated in that he was thinking about it but also snapped and the attack turned into a killing as he couldn't control himself. Why take a knife to meet your girlfriend? I think he was in the woods long before 4.50pm setting it up possibly with a change of clothes, gloves etc in a backpack that was disposed of later that night. If he'd told his friend about doing it I'm sure he considered all the scenarios. The time of death is certainly high risk but it all took place behind a high wall that allowed sufficient cover until he could "find" the body later.
Who knows for sure. Just my opinion.
It's definitely a tragic and strange case, with an abundance of anomalies, weird coincidences and many talking points. One thing that would lend credence to the 'LM snapping theory' is if he had had an argument with Jodi in school earlier that day; I've definitely read, on another forum, that he did, but no one has confirmed it either way and plus I've never read or heard about it in newspapers, online articles, Sandra's book or podcasts. If he'd argued with her in school earlier, there's a good chance the argument continued when they met up later at 1654 and LM lost all control at that point. The time of the death would also suggest that he snapped -- why would someone murder at 1715 Hrs? But, she did die in a secluded area, which would tend to suggest it was premeditated. Did LM coax Jodi to walk with him down the RDP west towards Newbattle? Was that what AB saw him doing - beckoning her down that path with his hand gestures? Of course, we can also factor in his previous violence (including being spotted at a party twisting a knife forcefully into Jodi's leg, causing her much discomfort), previous knife attacks on females, and his short temper episodes, and arrive at the conclusion that LM was a ticking time bomb. And, as I said in my opening post, he'd previously aired publicly his fantasies and knife knowledge to friends. He was coddled by CM, too, and was used to getting his own way . . . what could've went wrong?
Interesting you mention a back-pack and LM taking a knife to meet his girlfriend. I don't think he took a back-pack as I feel he'd want to be as inconspicuous as possible. He was in the habit of carrying knives in his parka jacket frequently (KT's own admission) and I'd imagine he had had knives in his possession in front of Jodi often. Likewise, the parka would hide gloves amongst other items (hence why AB said the pockets looked 'bulging'). As regards LM being in the woods long before 1650, I'm not so sure. Remember, he was on the family landline speaking to his Gran at the Caravan sales office at 1625 hrs (can't remember how long that call lasted). So, LM potentially could've been in the woods pre-planning at 1635 if on his bike or at 1640-1645 if on foot. I'm not sure. The one thing I am sure of is that LM murdered Jodi.