What is the purpose of memory? Most of us probably take our memory for granted, until it fails us and we can't find our keys or we forget to come home with the milk and bread like we promised, but let's take a minute and think about why we remember.
Imagine that you lived 5,000 years ago and went into the woods at night, and while walking along you came across a Panther! You turn and high-tail it out of there, safely arriving back at your camp. If you didn't have memory, what might you do the following night? Yeah, Panther food! Therefore, you remember not to go there again at night; but you will likely expand that to NEVER go into ANY woods at night. That way if you move camp 100 miles south, you won't meander into the waiting claws of a Panther, thanks to this aspect of memory. Also, if you communicate this information to your friends and family, they can use your memory of the event and implant it into their memory.
This is a survival aspect of memory, but it also shows the malleable and fragile nature of memory. Memory is not like a video recording of an incident, or else we would rationalize, "well, the panther was by THAT tree in THAT part of the woods, so if I go to THIS tree in THIS part of the woods I will be safe." So, we not only remember the specific incident but we also make generalizations from it as well. This is good for survival and avoiding Panthers, but it is not so good when we are investigating crimes. Memory likes to fill in the gaps of our knowledge, and if we really didn't get a clear picture of what happened, we will likely connect-the-dots so to speak. Or, if we didn't see or hear everything that occurred but we hear another witness talk about it after the fact, we may have a tendency to apply their information to our knowledge and contaminate our own memory of events.
Memory is what we access when we conduct investigative interviews, but how do we access that malleable, fragile entity without distorting the information? How do we know if the person is "connecting the dots" or if they actually saw and experienced everything they claim? How do we know that the information they are providing is from their experience, and not information they heard from someone else? There are no simple answers because memory is extremely complex, and there is much we don't know but we are learning more all the time through research.
Done improperly, the information from interviews can become distorted and inaccurate, and downright wrong! (Consider that about 75% of wrongfully convicted people were convicted of crimes they didn't commit in large part due to faulty witness memory!)
If you conduct interviews properly, you can draw out accurate and reliable information from people rich in detail, which solves cases and identifies bad guys, or leads to evidence that clears an innocent person or helps to prove the person is guilty!
When you think of how intrinsic our memory has been, and is, to our survival, it seems hard to believe that someone can "forget" the fact that they robbed a bank earlier that day, or "forget" that the girl he was on a date with said "STOP!" to his sexual advances, or "forget" the fact that a husband really killed his wife but he claims that she when shopping and didn't return home so he is filing a missing person report.
Well, barring a significant psychological disorder or some type of injury or trauma to their brain, they can't! That information is in their memory, and when a deceptive person tries to suppress that information by choosing to provide information contrary to their memory, we often see indicators of that within their speech, language and word choice, physiology, behavior and demeanor at times within the interview. That is as long as you know what to look for regarding reliable signs of deception as well as truthfulness, and if you are using effective questioning strategies such as Cognitive Interviewing and Investigative Statement Analysis so you can focus your questions at key areas within the statement or narrative.
Improper questioning strategies can lead to missed information because the investigator either focus on the wrong information or the wrong area of the individual's account, or they merely run down a list of questions to be asked and do not really hear or pay attention to what the person said or how they said it. Sometimes they even use techniques that cause behavior in the person they are talking to which, in their mind, looks "deceptive" and they start to pursue a line a questioning or lead into an interrogation based upon false assumptions that were generated by improper questions strategies.
It is crucial to maintain objectivity when conducting investigative interviews and to seek out and employ training that is based on scientific principles and sound research so that you are able to effectively probe the person's memory, extract accurate and reliable information and avoid Panthers!