Many have been baffled by the mistakes eyewitnesses made
The aftermath of the shooting of Jean Charles de Menezes at Stockwell Tube station has shown that eyewitness testimony may not always be as reliable as it seems.
On the day Mr Menezes was killed, a picture was quickly painted by eyewitnesses of a suspect who had vaulted over a ticket barrier, ran away from police, and had worn a bulky jacket that could have concealed a device.
Scotland Yard did nothing to dispel that impression, saying that the shooting had been "directly linked" to anti-terrorism operations, that Mr Menezes had been challenged but had not obeyed, and that the victim's "clothing and behaviour" had added to suspicions.
Over the last month, the image of Mr Menezes' conduct has been slowly dispelled, before being completely shattered by Independent Police Complaints Commission documents leaked to ITV News.
According to the documents, Mr Menezes was wearing a light denim shirt or jacket, walked through the barriers having picked up a free newspaper, and only ran when he saw his train arriving.
It has left many scratching their heads as to how the witnesses could have got it so wrong.
The reliability of eyewitness accounts of crime has proved a rich seam for psychologists and criminologists to mine over the years.
Presence of a gun
Conferring with others
Andrew Roberts, a lecturer in law at Leeds University specialising in evidence, said courts have recognised for a long time that eyewitness identification evidence is "inherently unreliable".
Two cases helped change the view in British courts, he said.
In 1969, Laszlo Virag was convicted of stealing from parking meters and using a firearm while trying to escape police officers. Despite his alibi and other contradictions, he was identified by eight witnesses as the man who committed the crime.
While he was in prison it was found another person had committed the crime and he was pardoned.
In 1972, Luke Dougherty was convicted of shoplifting after two witnesses picked his face out of a police album.
He was eventually cleared and both cases led to the Devlin Committee's investigation of identification evidence, which found that many witnesses overstated their ability to single out the right person.
But it is not just the thorny issue of recognising a face that confuses witnesses. Witnesses' recollection of every aspect of an incident can be contaminated by what they hear from other people.
Forensic psychologist Dr Fiona Gabbert has been working at Aberdeen University with Professor Amina Memon on the distortions in eyewitness recollection.
"Memories are very vulnerable to error. If you witness a crime and then read a local news report everything can be combined in your memory at a later date," she said.
Eyewitnesses can focus on a gun to the exclusion of other events
"It can be hard to distinguish between what you saw, and another source of information.
"If there are two people witnessing a crime it is very likely that you are going to ask the person next to you or say 'I can't believe what just happened'."
In studies at the university, subjects were shown very slightly different versions of the same event, such as a crime filmed from different angles.
The subjects are allowed to talk and then a statement is taken as if they are talking to the police.
Dr Gabbert said 70% of participants reported witnessing at least one thing they could not possibly have seen themselves.
Even when given a "source monitoring test", where the participants are asked to highlight what they saw and what might have come from other sources, 50% will report an item from their discussions with other people as their own.
"It is a true memory error - you are really thinking that you have seen it. It is horrifically scary," Dr Gabbert continued.
"There are criminal cases where witnesses identified the same innocent person. It goes to show your memory is so easily influenced. You discuss your memories with people every single day."
Not just other witnesses, but leading questions from journalists or investigators can also have an influence.
Detectives are always keen to speak to witnesses before reporters are able to get to them, fearing that sensational aspects will filter into their recollections.
And even without the influence of other people, retaining an accurate recollection of a complex event is not easy.
Mr Roberts said stress was a major factor in distorted testimony.
"When you see a very violent episode you are likely to be under great stress that adversely affects your ability to recall events accurately.
"There is also a well-known effect called 'weapon focus'. If you are watching an event where someone is brandishing a gun you don't recall as much information - psychologists think naturally your focus is on the weapon."
In a rolling news society, the effect of the media is powerful.
"One of the most dangerous things about the [Stockwell] shooting is the amount of information that is in the public domain. Witnesses on the tube are likely to have seen other witness accounts, the official version and information that followed from the police," Mr Roberts said.
A high-stress situation like the Stockwell shooting can confuse witnesses
"Where a witness is exposed to post-event information that tends to get assimilated into the memory."
Mr Roberts cited a study of Amsterdam residents who lived near the site of a 1992 plane crash that claimed 43 lives after a cargo jet smashed into an apartment block.
"The crash was never filmed. But quite a large proportion were adamant they had seen footage on TV and could recall images that were very graphic.
"They had got all this information from various sources but remembered it as an image they had seen on TV."
And setting aside all these factors, eyewitnesses can get things wrong because of interpretation.
Photo shop manager Christopher Wells, who said he saw the Stockwell victim vaulting a ticket barrier, has since conceded that he must have seen a plain clothes police officer.
How do you think that eyewitness accounts should be used?
It depends on the character of the witness. First she or he should be scrupulously be vetted and then allowed as the witness. A bad tool does not give a well done job.
Firozali A. Mulla, Dar-Es-Salaam, Tanzania
I once witnessed a shooting. I clearly remember a man loading a shot gun, but I hid when the shooting began. The shot gun was never shot, but a hand gun was used. Police never believed me when I said another weapon was involved. This was probably due to the fact that, because of the stress of the event, I was not very clear about anything else involved in the shooting (such as descriptions of those involved). Therefore, having been in one of those situations, I agree it if what you saw was really what you saw or if it came from someone else. To this day I still wonder whether the image I have in my head of a man loading a shotgun was reality or my imagination.
Colin Donaldson, Geneva, Switzerland
This just highlights the danger of the rolling-news services. All the TV companies are determined to 'get the facts to the public' first and consequently make big mistakes. I'd much rather wait until the journalist has had a chance to sift and verify the facts before telling me anything.
Whilst I treat witness statements with a certain degree of scepticism, I do the same for leaked reports. Leaking is a politically motivated exercise intended to sway thought or opinion. We do a disservice to our police force and Mr de Menezes by pre-empting the findings of this inquiry.
Ross Brown, London, England
I was asked to give an eyewitness account of an accident six months after it happened and I was astonished at how poor my recall was; even getting the vehicle colours wrong. Eyewitness accounts can be very unreliable if they are not recorded at the time of the incident and I agree they (eyewitness accounts) should only be taken as true if supported by other 'hard' evidence.
Shane McDermott, Derry
As has been explained, eyewitness accounts can be very unreliable, but this is often made worse in court by the fact that eyewitness accounts are also the most readily believed evidence by a jury. I feel that unless there is other evidence to back up these reports it should be emphasised to juries how unreliable eyewitness statements can be so injustices are less likely to occur.
Justin Key, Portmsouth, UK
Witnesses who get it wrong should never be blamed unless proved dishonest or fraudulent. Really the whole episode only illustrates the fascinating things that take place in that lump of soft tissue we call the brain. That a few exchanges of words, an odd line of text, an erroneous sound or some other titbit of data can be fed into our minds and translated and transmuted into living visual memory is incredible.
I think this raises issues for jurors as well as witnesses and shows how mindless journalism can have unseen negative effects on justice. More accountability for media bodies is needed.
Matt Young, Telford, UK
The papers know the information they print is taken literally by the majority. They should emphasise speculation to avoid misleading and panicking the public.
Mr M Ebrahim, Wolves, UK
People trust eyewitness accounts too much. In Finland, we have a locally well publicized murder case, from 1960 (45 years ago), with previously unheard of eyewitnesses testifying.
Veikko Punkka, Tampere, Finland
If eyewitness statements are not reliable and feed on collective experience, what does this do to our interpretation of other major events? Where do we draw the line? Would we dispute the guilt of the Lockerbie bombers? Should we deny the Holocaust? More work must be done to give us back our faith in eyewitness statements.
Neil Lithgo, Walthamstow, London
Absolutely fascinating article. I was amazed when ITV came out with "facts" after having been "fed" with info from "key" eyewitnesses and authorities via print and visual media. How wrong could one get? The lesson to be learnt by everyone is not to disseminate first information before they confirm it reliably.
Dr K Prasad, Ayr
Clearly eyewitness accounts are notoriously unreliable. This is quite understandable when people are witnessing shocking events. However, certain news agencies seem quite happy to report these accounts as "news" - without any verification. I think this is extremely dangerous and very misleading. I vividly remember on the morning of the July 7th explosions hearing reports that three buses had been blown up. Also, there was an eyewitness report of the Stockwell shooting that the suspect was wearing a bomb belt with wires hanging down. This kind of misinformation creates mass confusion and plays into the hands of the terrorists.
Lucho Payne, Bristol, England
Eyewitness accounts are so unreliable that they should only be taken as true if supported by other 'hard' evidence. I remember one televised experiment where several witnesses swore that the 'perpetrator' was black when he was white all along. Or maybe even that recollection is false..!
Steve Wooding, Liverpool, UK
If you're a witness and you get it wrong you should like be locked up as well.
Trevor Furber, Stevenage