By legal standards, hundreds of eyewitnesses is great evidence!
Actually no. Eyewitness is always one of the worst kinds of evidence, and quantity makes little difference. It remains very easy to argue that Bob just very closely resembles the killer. If we have actually good evidence of him being elsewhere that day, say he went to work and worked all day, maybe was on camera, clocked in and got paid, etc, then that would pretty soundly crush your hundreds of eyewitnesses.
Actually no. Eyewitness is always one of the worst kinds of evidence, and quantity makes little difference. It remains very easy to argue that Bob just very closely resembles the killer. If we have actually good evidence of him being elsewhere that day, say he went to work and worked all day, maybe was on camera, clocked in and got paid, etc, then that would pretty soundly crush your hundreds of eyewitnesses.