How do you think people involved in conspiracies are convicted? If the State needed a text stating "Hey Bob, do you want to come and help me kill Joe?" "Hey Sam, yes that sounds like a grand plan. Lets both go and kill Joe together."
The often have little to work with, so circumstantial evidence becomes key e.g driving past a crime scene shortly after a 20 minute phone call with one of the conspirators.
if we apply your extremely high burden of proof to every criminal case, no one would be in prison. Hence the reason it's beyond a reasonable doubt.
