The main reason why you can’t reach a decision on the assassination, beyond a reasonable doubt, is by design.
Bearing in mind that the most probable culprits are intelligence based, we need to expect plausible deniability, obfuscation and compartmentalisation.
I would suggest looking at the assassination using a similar framework to an intelligence analyst…assess the reliability of the evidence and assign it a probability of occurring and a confidence level.
Forget about beyond a reasonable doubt- it’s a wild goose chase.