When recently reading Dylan Schaffer's Misdemeanor Man, "a gripping, irreverent legal thriller", as the jacket cover rightfully states, I came across these helpful observations:
Most people believe that memory is like a video camera - you see something; it is stored, intact; and then at some time later you access the memory of the event, whole, like regurgitating a grape right after you eat it ... (however) memory is more like information stored in a computer, in small pieces that require internal organization and recombination when accessed.
Perception is by far the most important aspect of memory, because the quantity of information input has the greatest impact on a person's ability later to retrieve information. The most important factor is time - how much time the witness spends actually looking at the person's face. If you look at me for an extended period, and there are no distractions, and you are close enough to see me, you can take in a fair amount of information about my face and what it looks like: cheek structure, nose, size and position of eyes, hairstyle, jawline and so forth.
When a witness sees someone's face for three to five seconds, that permits perception of general features, race, gender, and perhaps a distinguishing feature or two. There is not enough time to see the specific features of a person's face. Also, stress plays a critical role. When a witness perceives someone during a period of great stress, the reliability of their memory goes down sharply. And there is another factor, which we sometimes call weapon focus, which usually means that when there is a gun involved in a crime, witnesses tend to be focused on the gun. Their perception of the face of the person holding the gun is less clear.
Events become part of a person's memory because they were suggested. People are not able to distinguish between what they actually remember, because they observed it, and what is in their brains because it was suggested. Suggested information is just as real in memory as information that was actually perceived.