Course taster

What is an expert witness?

While expert witnesses can be useful and there are several criteria in place to help ensure experts provide good, credible testimony, there are several issues with the use of experts within court.

One of these issues can be seen in the case of Sally Clarke, whereby faulty testimony by an expert witness caused a miscarriage of justice to occur (Davies & Beech, 2017). Sally Clarke had two sons who died weeks after their birth and just a couple of years from one another, and this was initially thought to be due to sudden infant death syndrome (or 'cot death'). However, Sally was later arrested on suspicion of killing her children and it was argued in court that she was engaging in Munchausen by proxy, whereby someone fabricates or exaggerates mental/physical problems of another person (in this case, of Sally's two sons) (Schreier and Libow, 1993). This was concluded after the expert witness, Professor Samuel Ray Meadow, conducted statistical analyses finding that the likelihood of two children from the same background dying from sudden infant death syndrome was extremely unlikely, at one in 73 million. Due to this testimony, Sally was found guilty of murder and imprisoned. However, it was later found that the statistical analyses used by Professor Meadow were not conducted properly, the methods and analyses used were not peer-reviewed, empirically tested or accepted by the wider community, and the figure of one in 73 million was grossly overstated (Bacon, 2003; Center for Statistics and Applications in Forensic Evidence, 2018). Later medical records for the children found that they did indeed die of natural causes. As such, Sally Clarke was eventually released from prison, but due to unreliable expert testimony she had been incarcerated for five years.

In cases where expert witnesses may be discredited or suspected of providing faulty information, a second opinion from another expert witness may be sought (Davies & Beech, 2017). For example, in one particular case where an expert was using psychometric tests, the expert judged the defendant as deliberately manipulating the tests. However, after a second opinion was sought, it was found that rather than attempting to manipulate the tests or mislead the expert, the defendant instead did not fully understand the questions being asked. This was then taken into consideration when deciding on sentencing options for the individual. In some cases, a method known as 'hot tubbing' may also be used, whereby experts from opposing parties meet to discuss and debate evidence together and provide testimony together, which can provide a more balanced account of the evidence.

Other issues

Another major issue, particularly in the UK, is that many expert witnesses who are used within courts may not actually be experts in their field. In a study by Ireland and Beaumont (2015), they found that one in 5 (20%) expert witnesses were not fully qualified in the field that they were commenting on and 90% of them were not currently practising in their field, and so lacked contemporary and up-to-date knowledge or experience. Many of them were also commenting on areas outside of their own expertise, and some made assessments on people through paper tests and without ever meeting the person being assessed in real life, meaning misdiagnoses are common watch the video summarising these issues - Channel 4 News, 2012).

How competent are 'expert' witnesses called to court?

View How competent are 'expert' witnesses called to court? video transcript

This is an important issue as expert testimony is often used in family courts and leads to key decisions being made regarding the custody of children, but these decisions will be poor if the expert is not truly an expert. Due to the nature of these court hearings, the testimonies are also often confidential and therefore outside of the public eye, making them more difficult to be held up to scrutiny. As such, within the UK there seems to be an issue of faulty expert testimony being used within the courts, although there is work to help alleviate these issues, such as creating an updated register of practising expert witnesses in the country and creating certification pathways for experts (see Dodier & Denault, 2017; Dror et al., 2013; Svider et al., 2014).

There are also problems with bias with expert witnesses. While experts are meant to be unbiased and provide balanced testimony regardless of the side that retained them (i.e. defence or prosecution), Murrie et al. (2013) found that experts do tend to show allegiance to the side that retained them, regardless of the evidence that is presented to them. As such, they can make biased decisions.

Expert witnesses can also sometimes provide testimony on topics which are highly contested and thereby may misapply research. For example, you may be aware of the work by Elizabeth Loftus, who was one of the first researchers to highlight that individuals can create false memories – that is, develop vivid recollections for events that never occurred. Her most influential work is the 'lost in the mall' study which found that individuals could be influenced to falsely remember being lost in a mall as a child (Loftus & Pickrell, 1995; also watch the video below summarising this study - Livesey, 2014).

Lost in the Mall (False Memory)

View Lost in the Mall (False Memory) video transcript

Other researchers have found that this can also occur for more dynamic and forensically relevant stimuli, whereby participants can also be influenced to falsely remember having committed a crime when they were younger (Shaw & Porter, 2015). Due to this line of research, there is a heated debate regarding repressed memories, with some researchers arguing that individuals can completely forget and later recover memories of traumatic experiences, while others argue that these 'recovered' memories are actually false memories – this debate has come to be known as the memory wars (Otgaar et al., 2020 ).

However, there are many limitations with the false memory research that has been conducted, with many studies using small samples, neutral memories that often have low emotional arousal and inconsistent means of measuring false memories, amongst many other limitations – the findings of most research also highlight that only a minority of participants come to develop false memories, although this is still a significant minority at around 30% (see Becker-Blease & Freyd, 2016; Brewin & Andrews, 2016). Due to these issues, the authors recommend caution when using such findings within the courtroom. However, researchers such as Elizabeth Loftus are regularly called in to provide expert testimony on the development of false memories, and this has been particularly controversial in cases of sexual abuse – for example, this research has been used to undermine the testimony of victims in the Harvey Weinstein and Ghislaine Maxwell trials, amongst others (Klasfield, 2021; Marks, 2021; The Guardian, 2020). This is not to suggest that the testimony of Loftus and others is inaccurate and should not be used - they are simply providing their expert opinion based on the most up-to-date research, but caution should be taken when judging certain evidence, particularly where it is contested. However, this calls into question a further issue with experts – can judges and jurors accurately assess evidence provided by experts?


Do experts bias jurors?

Think back to some of the biases we discussed during our unit on juries. Do some independent research to identify and read at least one article or piece of academic research that investigates the extent to which experts can have a biasing impact on juries. Do you think experts could be another factor that has a biasing impact on jurors? If so, how do you think they might cause bias?

Make a note (no more than 150 words) of your answers to these questions, as well as the reference for the research you have found, in your Personal Journal (The link to the Personal Journal is not available in this course taster).

After you have completed this, please select the Feedback drop-down to learn more:

There are many ways in which experts can have a biasing effect on jurors. We discussed many of these in the unit on juries, such as authority effects (having a doctor or expert title may cause jurors to consider an expert's opinion automatically correct), and jurors may be more influenced by the way an expert delivers their testimony rather than the actual information they provide (Davies & Beech, 2017).

If you would like to learn more about this, please watch the following video which goes into some of these biasing factors (UQx Crime101x The Psychology of Criminal Justice, 2014):

6.3 Expert testimony

View 6.3 Expert testimony video transcript