I honestly would not trust any "eyewitnesses" in about 80-90% of the areas where a critical incident would take place.
Some people may be honest or help you out but as a armed security officer & someone who worked in LE, I can say that many times bystanders make snap judgements, lie, are on drugs or alcohol or are so spun out they don't even know what happened.
Watch the local news stories of incidents in your area & see how witness statements vary.
CCTVs, smartphone cameras & audio recordings can help a lot.
Stay safe!
CF