Are you saying no one piece of evidence can be explicitly tied to one family member?I don't believe they've found physical evidence for any of them. They have 2 of the 4 that pled out. We don't know what other evidence they may have, in the voice recordings or otherwise.
They did eventually find the firing pin (in the well at Peterson Rd) that was a direct match of some of the casings found at some of the crime scenes, which was the final piece that led to their arrest.
But I guess without Jake’s proffer, no one piece of evidence does explicitly link any one person*. It was all circumstantial up to finding that firing pin.
No wonder it took so long to make an arrest - something I know we ALL had a hard time understanding.
*MOO Based on opening statements. I’m still catching up. May have missed something.