I find the question of whether he'll face the death penalty or life in prison a fairly convincing argument that the US federal judicial system has several very severe faults ...
1. He's clearly guilty of conspiracy, but the fact remains, he didn't kill anyone. That being the case, it is in the interests of any sane legal system to view it as a mitigating circumstance (in order to give other potential future conspirators an incentive to not pursue their plans to completion: if you can be executed for conspiracy as well as for carrying out the plans, there's no room for deterrence).
2. He may very well also be insane. Certainly his behaviour is suggestive of some serious problems.
3. The obvious witness nobbling should be enough to declare a mistrial. It also gives rise to questions as to whether there was prior interference in the earlier trial.