Are our memories reliable?

During the course of a criminal hearing or trial, witnesses are frequently called to give evidence about what they saw, heard or otherwise perceived about an event.

In the absence of other binding evidence, witness testimony can be the deciding factor in whether or not a person is convicted.

Witnesses are often required to take a ‘trip down memory lane’ to recall certain events or experiences, particularly when many months or even years have passed since the event in question.

But recent scientific studies have shown that memories are not as reliable as we may have previously thought – and in some cases, witnesses inadvertently construct or embellish past memories, which may directly affect the outcome of a criminal trial.

The Science Behind Memories

Memory is the mechanism by which the brain stores information about past events or experiences.

Scientists who study psychology and the workings of the brain’s nervous system have found that memories are not flawless records of past events, but rather mental constructions which may chop and change every time a person tries to recall a certain set of events.

For those lacking a scientific background, neurons are special nerve cells which transmit electrical and chemical signals between each other via special structures known as synaptic connections.

Long-term memories are created by the growth and maintenance of these neuron cells and synaptic connections.

Rather than being fixed or permanent connections, scientific studies have shown that synaptic connections are reconstructed every time a long-term memory is recalled.

This essentially means that there is the potential for a memory to be embellished, altered or distorted every time it is accessed.

As a particular memory is accessed more frequently – as for events that form the basis of criminal charges – the potential for it to be distorted becomes greater.

And the way that a memory may be distorted may depend upon the circumstances in which that memory is recalled and the needs of the ‘rememberer.’

As stated by leading psychologist Charles Fernyhough, ‘Memories might be about the past, but they are constructed in the present to suit the needs of the self.’

This means that the way in which a particular memory is recalled might depend on the present emotional state of the person, as well as other factors such as the context in which the event is remembered.

Science also suggests that memories of traumatic experiences are more prone to embellishment or alteration.

When a witness is approached by police to make a statement, there is a huge risk that that person’s memory may be distorted for a range of reasons – nervousness, anxiety, the desire to please police, or even a desire for revenge or to ensure that an alleged offender pays for their crime.

As the case goes along, the witness will surely think back to the period of the alleged incident, and there is potential for further distortion each time they do.

All of this is months or even years before they are required to take the witness stand before a room full of lawyers, members of the public and a jury, which can be a harrowing experience in itself.

False memories

In many cases, people have ‘remembered’ events which did not actually occur at all. These are commonly known as ‘false memories.’

False memories are often the result of a person’s exposure to new information after an event has occurred.

The potential for new information to trigger a false memory is increased where that information is deemed to be from a credible or reliable source, or where the person is exposed to it several times.

This can occur when a potential witness is questioned by a person in a position of authority, such as a police officer or a lawyer, about certain facts and circumstances which have not yet been established.

In these situations, a witness may inadvertently ‘fill in the gaps’ in their memory with information relayed to them by others.

How Does the Law Deal with Issues Surrounding Memory?

Assuming that the science behind memory is accurate, the above discussion illustrates the dangers in relying solely on witness testimony.

The law has attempted to deal with these issues in several ways.

Importantly, there are legal rules which state that a person can only give evidence about something that another person told them where the other person made the statement about an event which was ‘fresh in their memory.’

So how does this rule apply?

The case of Graham v The Queen provides a useful example.

In that case, a female made a complaint to her friend some six years after the event that her father had allegedly sexually assaulted her when she was 9 and 10 years of age.

The friend, however, was prevented from giving evidence during the trial because the complaint was not made when the events were fresh in the complainant’s memory.

The High Court held that the phrase ‘fresh in the memory’ refers to a memory about a recent or immediate event.

Generally, this refers to matters which have occurred in the space of several hours or days, however there is not set ‘time limit’ – each case must be assessed individually.

In deciding whether or not a memory is ‘fresh’, a court is able to consider factors such as the nature of the event in question and the age and health of the person, but the main deciding factor is how recently the event occurred.

The High Court held that evidence of an event which occurred years beforehand will only be admitted in rare cases where ‘some special circumstance or feature’ can be proven.

Alternatively, where issues about a person’s memory arise in criminal trials, lawyers have been known to call ‘memory experts’ to give expert evidence before the courts.

A lawyer seeking to rely on the evidence of a ‘memory expert’ must prove that they have ‘specialised knowledge’ before the court will allow that person to give evidence.

Memory experts are particularly useful in jury trials, because lay people often have limited understanding of how memory works and the factors that may affect its reliability.

Memory experts can help to explain these concepts and assist the jury to understand the problems with recollections.

In other cases, a judge may warn the jury that certain evidence is unreliable, and may caution them against accepting the evidence and attaching too much weight to it.

This is particularly useful where evidence is given by a child, because children are generally thought to be unreliable witnesses.

While these provisions make some headway in addressing the problems associated with memory, there are still obvious problems in placing too much weight upon evidence based upon what a person recalls.