In certain countries, such as the United States, the law states that the testimony of the victim or a witness is comparable to the weapon of the crime as evidence to . But are the memories of witnesses a sufficiently objective and reliable key to solving a case?

The weapon is physical and tangible evidence from which very useful information can be obtained: who owned it or who had wielded it by the prints on it. But the memory of the human being is not something objective and immutable. It does not work like a camera, as several psychological studies have shown. In fact, psychologist Elisabeth Loftus proved throughout the 20th century that it is even possible to create false autobiographical memories within people’s minds.

Creating false memories

Almost all our personal memories are modified, disturbed by experience and learning . Our memory does not elaborate a fixed and detailed memory of an event, on the contrary we usually only remember something that we could call “the essence”. By remembering only the basics we are able to relate memories to new situations that have some similarity to the original circumstances that gave rise to the memory.

In this way, the functioning of memory is one of the pillars that make learning possible, but also one of the causes of the vulnerability of our memories. Our memory is not perfect, and as we have often found without surprise; it is fallible.

Long-term memory and recall

It should be noted that our memories are stored in what we call the long-term memory . Every time we bring out a memory in our everyday life, what we are doing is building the memories with pieces that we “bring” from there. The transfer of memories from long-term memory to the operating system and consciousness is called retrieval, and it has a cost: every time we remember something and subsequently bring it back to the long-term store, the memory is slightly altered when it is mixed with the present experience and all its conditioning factors.

Moreover, people do not remember, re-elaborate, construct anew the facts each time they verbalize them, always in different ways, always generating different versions of the same event. For example, recalling an anecdote between friends can provoke a debate about the clothes one was wearing that day or what time exactly one arrived home, details that can end up being modified when we bring the memory back to the present. Details that we do not pay attention to because they are not usually significant, but which are key in a trial.

The effect of emotions on memory

Situations of emotional stress also have a very powerful effect on the memory of witnesses and especially on the memory of victims. In these situations the impact produces a more or less permanent damage to the memory. The consequences are in the tremendously vivid recollection of small details and a deep void about actions and circumstances that may be more important.

Peripheral memories are more plausible than central ones when faced with an event with great emotional impact . But, especially, emotions bathe and soak the memories with subjectivity. Emotions cause that which has hurt us to appear much more negative, perverse, ugly, obscene or macabre than it objectively is; and in contrast, that which is associated with a positive feeling seems more beautiful and ideal to us. For example, curiously enough, no one hates the first song they heard with their partner, even if it was played on the radio or in a disco, because it has been associated with the feeling of love. But we must not lose sight of the fact that, for better or worse, objectivity in a judgment is of prime necessity.

A shocking injury, such as rape or a terrorist attack, can create a post-traumatic stress condition in a victim, cause intrusive memories in the victim and also blockages that make it impossible for the victim to recover the memory. And pressure from a prosecutor or police officer can create memories or testimonies that are not true. Imagine a paternalistic police officer saying something like, “I know it’s hard, but you can do it, if you don’t confirm it, that man will go home free and satisfied. An insidious cop or prosecutor, who pushes too hard for answers, will bring up a false memory. Only when the victim is able to distance herself emotionally from the event and play it down will she be able (perhaps) to get the memory back.

To trust the memories…

One technique for avoiding post-traumatic stress and blockage is to elaborate or tell someone the facts as soon as they happen. Externalising the memory in a narrative way helps to make sense of it .

When it comes to witnesses, there are always more plausible memories than others. It never hurts to have a forensic expert assess the value of the memory before allowing it to testify in a trial. The optimal level at which we remember is when our physiological activation is medium; not so high that we are in a state of anxiety and stress as can be found in an exam; not so low that we are in a state of relaxation that borders on sleep. In such a case a crime causes a high physiological activation, an emotional stress that is associated with the event and that therefore arises every time we try to remember, diminishing the quality of the memory.

Therefore, the memory of a witness will always be more useful than that of the victim as it is subject to less emotional activation . It should be noted, as a curiosity, that the most plausible memory of a victim is the one that focuses on the object of violence, that is, the weapon.

Bias in legal proceedings

On the other hand, we must take into account that, sometimes, the lineups and interrogations can be unintentionally biased . It is due to this bias towards injustice, or because of ignorance of the effect of asking a question in a certain way or ordering a set of photographs in a specific way. We cannot forget that police officers are human beings and they have an aversion to crime as great as that of the victim, so their aim is to put the guilty party behind bars as soon as possible; they think biasedly that if the victim or the witness says that one of the suspects looks like the guilty party, it must be him and they cannot let him go.

There is also this bias in the population that dictates that “if someone is a suspect, he or she will have done something”, so there is a widespread tendency to believe that suspects and defendants are blindly guilty . For this reason, when faced with a series of photographs, witnesses often tend to think that if they are presented with these subjects it is because one of them must be the guilty one, when sometimes it is a question of random individuals and one or two people who slightly coincide in certain characteristics with those described to them (which in fact do not even have to be true). This mix of police, prosecutor, judge, jury, witness, and public bias can result in such a combination that an innocent person is found guilty, a reality that occasionally happens.

Of course I do not mean that any testimony should not be assessed, but it should always be done by evaluating its veracity and reliability. It must be borne in mind that the human mind is often wrong and that we must distance ourselves emotionally from suspects before judging them in order to do so objectively, taking into account not only reliable witnesses but also rigorous evidence.