Judging the accuracy of witness evidence

I’m taking a detour in my reading at present into the world of memory. There is a considerable amount of literature out there in relation to police investigations, but not so much for workplace investigations.

One book that I’ve found particularly user-friendly is Daniel Reisberg’s The science of perception and memory: a pragmatic guide for the justice system. (The link is not to Amazon, but to Better World Books, which is a “greener” option when buying books).

The book has made me pause and think about the need for investigators to have a checklist to assess the potential for memory error in witness testimony. If such a checklist would exist, it would contain the following:

1. Whether neutral questions were asked by the interviewer. What may surprise you, is that asking questions such as “what were you paying attention to during this event?” will actually increase memory error.
2. The extent of the witness’ spontaneity in providing their memories. The less questions we ask as investigators, the less we will potentially contanimate their memories.
3. The extent that the event was clearly observed (e.g. viewing angle, amount of light, the complexity of the situation, the amount of attention that was being paid).
4. Contamination (otherwise known as source confusion): our memories may have been influuenced after talking to others about the event – particularly if it’s someone we trust (“intrusion error”); or we may have filled the “gaps” in our memory, unconciously.
5. The urgency in which the witness is asked to recall a memory: the more pressure we put on a witness, the more they will “fill the gaps” with erroneous memories. This has a technical term: imagination inflation.
6. Motivation: the drivers behind the witness’ desire for their recollections to be heard (which are not always noble)
7. Plausability: whether the recollection is believable or not (think: being abducted by aliens).
8. Retentional retrieval: it is harder to recall memories over time, and our memories fade quickly at first; we may also fail to recall a memory, as we’ve not been given the correct “retrieval cues”.
9. After the event memory: when someone recalls an event that they didn’t think was significant that time, but they do now. The chances are that they didn’t lay down a complete memory, and therefore unconsciously they will have “filled the gaps” as they sought to retrieve the partial memory.
10. Claiming a flash-bulb memory: when a witness claims that the memory is as clear as the day that it occured….it’s not.
11. The level of stress that a witness has or did experience: stress has a negative impact on memory.
    

Lack of consistency in recalling the details of an event, does not mean that a witness is not credible. Research shows that the other elements recalled by witnesses could be accurate. Equally, just because someone seems super-confident in their recollections, it doesn’t mean that their memories are more accurate than someone feeling less confident.

It should also be noted that many of the above (but not number 5) are “honest memory errors”. As such, witnesses should not be berated for their mistakes in accurately recalling an event, as human beings are unable to spot what is a “real memory” and what part of the memory has been contaminated, unconsciously. And witnesses won’t recall every part of an event – they will only recall what was relevant to them at the time.

I should quickly mention that Reisberg makes a disclaimer: that despite the concerns around memory error, memories are often more accurate than they are inaccurate. So, maybe I’m over-thinking the need for a checklist?

Hit vs Smash. The impact of leading questions on memory recollection

Through my reading about memory investigations, I’ve recently come across the same piece of research twice: undertaken by Loftus and Palmer in 1974, the research shows how the phrasing of a question can impact on a witnesses recollection.

In brief: witnesses were asked to watch a short film clip of two cars who collide. Afterwards, the witnesses were asked to recall their memories, in detail, of what they had watched. For one set, the witnesses were asked “How fast were the cars going when they hit each other?” The other set were asked “How fast were the cars going when they smashed into each other?”

By changing just one word, the answers of the two groups differed: Group A (the “hit” team) suggested a slower speed than those in Group B (the “smash” team). The researchers concluded that the use of a subjective word, such as “smash” had a demonstrable (and potentially erroneous) impact on witnesses’ recollections.

None of the witnesses were conscious that the way the question had been asked influenced their answer. We are all triggered unconsciously by language. As investigators it is important that we are not just neutral in our mindset, but how we ensure neutrality through our language when we interview witnesses.

Equally, as investigators we can also be triggered by language. Investigators should pick up on emotive or subjective words and question the witness further: what to they mean? how can they qualify that statement further? Sometimes, emotive language is useful witness testimony – and you wouldn’t expect a witness to be neutral through-out their interview.

From time to time, I suspect that we, as investigators, will make assumptions when we hear emotive language – that we know what a witness means because we have also observed the same. We should still stop and ask. Otherwise, we could be accused of overlaying the witness testimony with our own unconsious bias.