I would consider that a reasonable motive, but I think you just have no evidence at all other than the fact that AK met RG when he visited the guys downstairs. There are no texts between them and young people nowadays texts all the time. I think you would need evidence of someone seeing the three together (other than heroin addict), texts between them, someone saying AK mentioned her friend Rudy, emails, etc.
But there is nothing and no evidence at all of a relationship between RS and RG that they even met each other. It is very hard to prove a murder of 3 defendants when there is not even clear evidence that they knew each other. Indeed, I don't think there has even been a case, almost always codefendants are lovers, business partners, etc.
If RG was their drug dealer, it would make the case more plausible. But then why no AK and RS in the room? They would have all went in that room. Why would there be nothing of the two of them? Indeed I think if they had been in that room, they would have tried to explain it - ie RS would have said he once went in the room to talk to MK so as to give an alibi in case his DNA was found. But they did nothing of the type. Both denied ever going in that room and no evidence was found.
Even if they were there doing the murders, you have no evidence AK and especially RS did any stabbing. That knife was not the murder weapon as it strains credibility to even think that it would not have blood DNA all over it nor does it match the wounds. Moreover, at the very least, there is nothing tying RS to the murder. Even if a sex game, maybe he tugged at her bra, that does not mean he was any way involved in the stabbing. They have nothing connecting him to the stabbing and I think bc of that if he was really there and AK did in fact do stabbing he would have turned on her a long time ago. He would have said they played sex game then she and RG started stabbing, he tried to stop them but feared for his own life. If he turned on AK, he would be free now and would be making millions from the tabloids giving dirt on AK.
We focus so much on AK but what really connects RS? Nothing except the bra and there could be alot of reasons for that, sloppy work being the most likely but he could have hugged her, it could be transfer DNA, etc.
I wonder why RS lawyer did not try to separate his trial. Without AKs statement and some of her actions in evidence, they have a really poor case against him...