Time elapsed between the event and the interview. A critical aspect of gaining the best account of events from any witness is making sure that the interview happens at the earliest opportunity. It is a practice in police investigation to make every effort to identify and interview witnesses as soon as possible.
As a simple exercise to demonstrate the importance of finding and interviewing witness quickly, take a piece of paper and to the best of your ability, write down the details of your day starting at the beginning of the day three days ago.
- What did you do?
- Where did you go?
- Who did you see?
If you are like most people, you have some level of daily structure to your life. From that structure, perhaps you will recall you got out of bed at a usual time. Maybe you went to work or stopped at the gym or at your favourite coffee shop on the way to work.
These benchmarks of your daily routine may be easily remembered.
But, on your way to work, did you happen to see a green van with extensive damage to the front end on the street near your home?
Of course, this is a fictitious question, but this would be the kind of inconsequential daily observation information you might be asked to recall by police canvassing for witnesses to a crime.Understanding this time limited aspect of human memory, investigators need to consider how much weight they can place on the accuracy of information being recounted by a witness. If a witness is providing a remarkably accurate recollection of something being recounted from any distance in the past, it is a good idea to ask that person how they can recall what should be a mundane event with such a degree of accuracy or clarity. If they are correct, the witness will sometimes provide a memory trigger that made them notice and causes them to recall. For example, a witness may answer, “Yes, I remember that green van with all the damage to the front end because my brother has a green van just like that and I looked at the driver and saw that it wasn’t my brother. I looked at it even closer because I had never seen that van on my street before.”