PSYCHOLOGISTS SPECIFICALLY trained in legal issues, as well as those with no formal training, are often called by legal parties to testify as expert witnesses.
In criminal trials, an expert witness may be called to testify about a vast range of issues such as eyewitness memory, mistaken identity and fitness to plead (in court) - to name just a few.
Psychologists who focus on clinical issues often testify specifically about a defendant's competence and intelligence. More general testimony about perceptual issues may also come up in trial.
The term ‘legal psychology’ has only recently come into usage, primarily as a way to differentiate the experimental focus of legal psychology from the clinically-oriented forensic psychology.
Together, legal psychology and forensic psychology form the field more generally recognized as ‘psychology and law’. Following earlier efforts by psychologists to address legal issues, psychology and law became a field of study in the 1960s as part of an effort to enhance justice.
Psychological issues can have a great bearing on the outcome of a trial – take eyewitness memory, for instance. This can be divided into three stages:
Stage 1: At the time of the incident
When witnessing an incident, initial information is memorised, however, research demonstrates that the accuracy of such information can be influenced by several factors.
Take the duration of the incident for example. In an experiment carried out by Clifford and Richards (1977), an individual is instructed to approach a number of police officers.
They are told to talk to the officers for either 15 or 30 seconds. Thirty seconds after the conversation has been completed, the experimenter asks the police officer to recall details of the person they’ve just been speaking to using a 10-point checklist containing questions about the person’s appearance such as hair colour, facial hair etc. The results of the study revealed that in the longer 30 second condition, police were significantly more accurate in their recall.
Stage 2: Time between witnessing an incident and recall
This stage is concerned with the period of retention between seeing an incident and the subsequent recollection of that incident.
Research has consistently found that the longer the time between witnessing an incident and recalling it, the less accurate the recollection of that incident becomes. There have been numerous experiments, usually related to a staged event, that support this contention.
Malpass and Devine (1981), for example, compared the accuracy of
witness identifications after three days (short retention period) and five months (long retention period).
The study found no false identifications after three days, but after five months, 35% of identifications were false.
Stage 3: Giving evidence
The final stage in the eyewitness memory process relates to the ability of the witness to access and retrieve information from memory. In a legal context, the retrieval of information is usually elicited through a process of questioning and it is for this reason that a great deal of research has investigated the impact of types of questioning on eyewitness memory.
The most substantial body of research has concerned leading questions, which has consistently shown that even very subtle changes in the wording of a question can influence subsequent testimony.
One of the most notable researchers in this field is Elizabeth Loftus who has been investigating eyewitness testimony for over 30 years. In one of her studies, participants witnessed a film of a car accident and were asked to estimate the speed of the cars involved.
One group of witnesses were asked to estimate the speed of the cars when they ‘contacted’ each other, whilst a second group of witnesses were asked to estimate the speed of the cars when they ‘smashed’ each other. On average the first ‘contacted’ group gave an estimate of 31.8 miles per hour. Whereas, the average speed in the second ‘smashed’ group was 40.8 miles per hour.
Fitness to plead
Psychologists are increasingly being asked to comment on fitness to be interviewed and fitness to plead. The outcomes and accuracy of these assessments greatly impact on the criminal justice process.
In the law of England and Wales, fitness to plead is the capacity of a defendant in criminal proceedings to comprehend the course of those proceedings. The concept of fitness to plead also applies in Scots law. Its United States equivalent is competence to stand.
If the issue of fitness to plead is raised, a judge may find a defendant unfit. This is usually done based on information following a psychiatric evaluation.
In England and Wales the legal test of fitness to plead is based on R v Pritchard. The accused will be unfit to plead if he is unable to:
- Comprehend the course of proceedings on the trial, so as to make a proper defence;
- Know that he might challenge any jurors to whom he may object;
- Comprehend the evidence
- Give proper instructions to his legal representatives.
If the issue is raised by the prosecution, the prosecution must prove beyond reasonable doubt that the defendant is unfit to plead. If the issue is raised by the defence, it need only be proved on the balance of probabilities.
In Scotland the test is based on HMA v Wilson, and has two elements:
- To be able to instruct counsel and
- To understand and follow proceedings.
If the judge determines that the defendant is unfit to plead, evidence will be heard and the jury will be asked to determine whether the defendant did the act or made the omission charged against him/her as the offence.
This process avoids the detention of innocent persons in hospital merely because they are mentally unfit. It has been held that the reference to the ‘act or omission’ means that the jury should not normally consider whether the defendant had the requisite ‘mens rea’ (the Latin term for‘guilty mind’) which is usually considered one of the necessary elements of a crime.