What matters is this:
RG was there before ANYONE else. He stated it himself on the skype call, before he even got arrested. What he did between the time he got there and roamed around and returned, we only have his word for. We know for a fact that MK arrived next. It's indisputable, since at 842pm, AK was at least a 5-7 minute walk from there, talking to RS's friend about the suitcases.
Considering that it took time for AK to talk to the friend, and she probably was in no hurry---IF---she were returning to the house, we can glean from that little bit of information is what is the most reasonable theory. That is, RG was there, somewhere, when MK arrived home and it was just the two of them.
Any other scenerio causes AK to rush the conversation with RS's friend, fly out the door and rush home to somehow meet RG right outside her house at the same time MK arrived home. It would then cause AK to have to change her plans of whatever she'd come home to do and decide she was just going to chill with RG, a man she NEVER chilled alone with before, instead of say, getting her clothes to return to RS's. Surely she didn't tell him see ya tomorow because they'd spent every night together at his house.
So logic tells us that it's not reasonable to assume AK returned home from the murder, saw RG in her yard or at the basketball courts, or anywhere else and up and decided to change her entire night's plan without calling RS. Logic tells us that they were not planning to spend the night at the cottage because they'd spent each night at RS's house.
So I don't see the scenerio, given that RG has already informed us that he'd been lurking around that house. He'd been lurking around that house before AK even knew she had the night off. Why is that? Surely he wasn't meeting RS alone. They didn't even know each other.
This is one of the main things I don't understand about any guilty theory. According to 90% of the evidence, MK died before 10pm. So what's the logical scenerio that gets AK and RS involved in it between 9pm and 10pm, (I'm giving SK 18 minutes to talk to the friend, confer with RS and walk home by 9pm.)