I found it quite amazing that the Captain is only ever burdened with the final decision AFTER a questionable passenger is boarded.
Another example is deportees..... The number of times I have been presented with a deportation order (usually a DEPU) to find that in his notes he has a history of violence. Some REMF in the company is supposed to vet these cases before they get to the coal face. Following my offload of one such DEPU I was informed by a manager that I should not open the deportation order..... I asked if that was the same envelope addressed to the Captain of flight xxx from HM Border Force ordering his deportation?