As time passes, details in memories degrade. The memory of lunch with a friend is still with you a week later, but do you recall the color of the shirt he wore?

Ask a witness to a crime what they saw immediately following the event and they will recall more detail than they would if you waited several days or a week to ask them to recount their memories. It seems a simple concept, but often witnesses are only interviewed briefly at the crime scene. The full interview may not take place for several days. By this time, many of the important details about people and events have been forgotten. The more time that elapses between the event and being asked to fully recall the details, the less accurate the report is likely to be.

With funding from the British Academy and working with police forces in England and Scotland, Dr Lorraine Hope from the University of Portsmouth and collaborators Dr Fiona Gabbert (University of Abertay) and Professor Ronald Fisher (Florida International University) have developed the Self Administered Interview. Tests conducted using simulated crime scenes, showed that recall concerning the events was 42-44% more accurate when witnesses used the SAI following the event. A second test showed that even a week later, accuracy for details and people involved was 30% higher for those who used the SAI than for witnesses who were simply asked to “tell us all that you can remember”.

Memory decay happens very quickly in the first few days following an event and eventually slows and levels off. This means that over time, witnesses memories of events will include the basic framework of the event but be devoid of details they might have recalled if they had the opportunity to record their memories before the information is forgotten. Going over the details sooner helps strengthen and protect the memory, guarding it from the natural process of forgetting.

Scientists develop new tool to ‘freeze’ crime scene memories