I shall choose to look at it this way...
If the M's are truly guilty (and I think the majority of us on here believe that they are), then there can be nothing more terrifying than waiting for the axe to fall...always looking over your shoulder, always feeling a pit of dread in your stomach when you see a police officer....always wondering if you're going to be arrested and charged with murder at any time.
THEN, one day, when you're least expecting it, you're re-arrested for murder and this time you're not so smug and you know they have the evidence now to prove it.
We just have to wait for that one day.
jmo