I dont really believe the letter story; no letters shown, no proof. It sounds terribly convenient to say 'oh he signed them SBTC.' The SBTC also was linked to Patsy- SAVED BY THE CROSS. And it was significant to John Ramsey as well.
I think Karr is a fruit loop, not a killer. Not yet anyway. I know more about this case than he does.
Alot of the original DNA/fingerprints etc was tampered with when a)john ramsey picked up Jonbenets body & b)when patsy threw herself over Jonbenet's body.