If SM is paying TM's tab, beginning with his obstruction behaviors and continuing to withhold the bigger story, then he earned his way to prison yesterday. But if he's truly not complicit in the actual crime, then what is the reason for continuing to keep his mouth shut? The stakes for keeping silent are so high.
I guess we'll see, and I agree that the relationship may implode and who knows where that will lead. But, she's either convinced him that there's a price so hefty for talking that it would equal his annihilation, or, he's in so deep alongside her that he can't give her to the state without offering up himself. I do know from witnessing it in a very personal situation that Narcissists, which I believe TM is, are masters of creating trauma bonds via children, threats to all aspects of the victim's life, and gas-lighting so severely that what one might normally do is not what one does in a relationship with a Narc.
I don't say this to give SM any passes. If the pay phone call was in fact a lure, then he was in it from the beginning, although TM may have set him up through some theatrical lie to get her own access to Heather. I think that given what she is, it's hard to know to what extent SM is the same, or not. Again, I'm not reducing him to a hapless victim, but Narcissists are deadly (as the absence of Heather reinforces) and I think that the TM/SM relationship and this crime are both so loaded with secrets and psychologically violent dynamics and layers that it's anyone's guess who owns what, to what extent, and for what reasons. I do think TM is center-stage no matter what the details of the greater story.