Would a polygraph test (or multiple ones in case of a result of “inconclusive”) for each of the eyewitnesses (and officer Darren Wilson, too, as there would undoubtedly be calls to keep this balanced) be administered to ‘get to the bottom of this’?
A polygraph would most likely not be conclusive. For one thing, polygraphs are pretty unreliable and relatively easy to beat. More importantly, though, the most that a polygraph shows is that a person is intentionally lying. If an eyewitness genuinely believes that he saw what he says he saw, then a polygraph will prove nothing, even if the witness’s recollection is wrong (as it often is).