I read about a drill where a group of people are assembled in one place for one reason or another. Then they stage a crime in the middle of the assembly. After the crime is over they ask each person to write down what they saw.IOW- they do not know in advance they are going to witness something.I think also jurors need to be shown some of the new studies coming out about eyewitness testimony and it's unreliability. At least when it comes to recognizing strangers. I don't think it applies when the person sees someone they know killing someone, obviously that's pretty clear, but it usually is a problem when they are asked to pick a stranger out of a lineup who they saw near the crime or committing a crime. It's just fascinating and scary the way the human mind and memory works, I think we have so much still to learn about it...
The differences in what each person saw is amazing. Eyewitness testimony can be sketchy, as the mind is a funny thing and visual memory is not necessarily reliable. people have been falsely convicted on eyewitness testimony simply because the witness was mistaken.
Additionally, circumstantial-forensic evidence is often used to exonerate people that have been convicted on eyewitness testimony.
here is a 60 minutes I watched not too long ago about this very thing.
>>But there is one type of evidence that's even more persuasive: DNA. There have been 235 people exonerated by DNA in this country, and as 60 Minutes and correspondent Lesley Stahl first reported in March, now a stunning pattern has emerged: more than three quarters of them were sent to prison at least in part because an eyewitness pointed a finger - an eyewitness we now know was wrong.<<
http://www.cbsnews.com/stories/2009/03/06/60minutes/main4848039.shtml