Syag, how do you know the racial identity of the witnesses? Anyway, there were a lot of witnesses, and most of them did not really corroborate Wilson’s story.
However, some did, and if these witnesses were believable, then that creates enough doubt to justify the decision not to indict. It all comes down to who you believe (a judgment one is not supposed to make on the basis of race, quite rightly).
In law there is certainly such a thing as a close cases. Prosecutors and judges encounter them all the time. Does reasonable doubt exist? Reasonable suspicion? Is a contract term unconscionable? I’m not saying this is necessarily a close case, because I haven’t looked at all the evidence, but it seems like it might have been, since again it has to do with how many witnesses said what, who is believable, etc.