I understand all that, but she needs to be able to put a name to this person, so he could be subpoenaed to state if he did that or not, and if he did why? Otherwise it is just someone saying I saw. It is also a PROVEN fact what someone thinks they saw is not always correct.
" Research has found that eyewitness-identification testimony can be very unreliable. ... Although witnesses can often be very confident that their memory is accurate when identifying a suspect, the malleable nature of human memory and visual perception makes eyewitness testimony one of the most unreliable forms of evidence."