Okay. Why marry someone decades younger than yourself and not only be shocked, but stoop to murder when they resort to finding you too old for you someday?
Did you not see this coming? It's almost kismet! 
It happens in marriages when people are the same ages no less.
I understand the disappointment, disillusionment, and pain. But, do you deserve to go to prison over either of these two lowlifes???
There's a Higher Power and They will get EXACTLY WHAT THEY DESERVE.