Can we trust the testimony of witnesses and victims of crime?

False memories and other obstacles cast doubt on the credibility of witnesses and victims.

In some countries, such as the United States, the law states that the testimony of a victim or witness is equivalent to a murder weapon as evidence of a crime.a. But, But are the witnesses' recollections 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 human memory is not something objective and immutable. It does not work like a camera, as several psychology researches have shown. In fact, psychologist Elisabeth Loftus proved throughout the 20th century that it is even possible to create false autobiographical memories inside people's minds.

Creating false memories

Nearly all of our personal memories are modified, disturbed by experience and learning.. Our memory does not elaborate a fixed and detailed recollection of an event, on the contrary we only tend to remember something that we could call "the essence". By remembering only the basics, we are able to relate memories to new situations that bear some resemblance 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 to our surprise; it is fallible.

Long-term memory and memory retrieval

It is worth noting that our memories are stored in what we call the long-term memory. Every time we bring up a memory in our everyday life, what we are doing is building the memories with pieces that we "bring back" from there. The passage of memories from long-term memory to the conscious, operating system is called retrieval, and it comes at a cost: each time we recall something and subsequently bring it back to the long-term store, the memory is slightly altered by mixing it with the present experience and all its conditioning factors. and all its conditioning factors.

Moreover, people do not remember, we rework, we construct the facts anew each time we verbalize them, always in different ways, always generating different versions of the same event. For example, recalling an anecdote between friends can lead to a discussion about what clothes one was wearing that day or exactly what time one arrived home, details that may 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 more or less permanent damage to the memory. The consequences are in the tremendously vivid recall of small details and a deep emptiness about actions and circumstances that may be more important.

Peripheral memories are more plausible than central ones in the face of an event with great emotional impact.. But, especially, emotions bathe and soak memories with subjectivity. Emotions make that which has hurt us seem much more negative, perverse, ugly, obscene or macabre than it objectively is; and on the other hand, that which is associated with a positive feeling seems more beautiful and ideal to us. For example, curiously enough, nobody hates the first song they heard with their partner, even if it was played on the radio or in a discotheque, because it is 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 a rape or a terrorist attack, can create in a victim the condition of post-traumatic stress, provoke intrusive memories in the victim and also blocks that incapacitate him/her to recover the memory. And pressure from a prosecutor or a police officer can create memories or testimonies that are not true. Imagine a paternalistic policeman 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 happy. An insidious cop or prosecutor, pushing too hard for answers, will surface a false memory. Only when the victim is able to emotionally distance himself from the event and downplay its importance, will he (perhaps) be able to recover the memory.

To rely on memories...

A technique to avoid post-traumatic stress and blocking consists in elaborating or telling someone about the events as soon as they have happened. Externalizing the memory in a narrative way helps to make sense of it..

When it comes to witnesses, some memories are more plausible than others. It never hurts to have a forensic expert evaluate the value of the memory before being allowed to testify in a trial. The optimal level at which we remember is when our physiological activation is average; neither so high that we are in a state of anxiety and stress as can occur in an exam; nor so low that we are in a state of relaxation bordering 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 is worth noting, as a curiosity, that the most plausible memory of a victim is the one that focuses on the object of violence, i.e., the weapon.

Bias in judicial processes

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

There is also this bias in the population that dictates that "if someone is a suspect, he must have done something", so that there is a general 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 party, when sometimes they are random individuals and one or two people who slightly coincide in certain characteristics with those that have been described (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 to say that any testimony should not be evaluated, but it should always be evaluated for truthfulness and reliability. We must bear in mind that the human mind is often mistaken 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.