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We’re all prone to cognitive bias and allowing our views to shape our thoughts and behaviour. But what happens when cognitive biases present themselves in legal proceedings? Below we examine different types of cognitive biases, how they can shape trials and legal decisions and how lawyers can challenge them.
Written by Grant Longstaff. Published 16 October 2026.
What is cognitive bias?
A cognitive bias is a systematic error in thinking which occurs as we process and interpret information and can affect our decision making and conclusions. This means perceptions, rather than the objective truth, can shape a person’s thoughts and behaviour in the world. These biases mean we’re all susceptible to distorting reality, irrational thinking and inaccurate thinking.
Types of cognitive bias
Since the idea was first presented by psychologists Amos Tversky and Daniel Kahneman in 1972 a comprehensive list of cognitive biases has emerged. This list constantly evolves as more research is conducted and we better understand cognitive function and decision making. Estimates put the number of biases between 100 and 200, though debates continue as to whether all these biases are a result of human cognition or adaptive behaviour.
It’s impossible to cover every cognitive bias proposed, though Wikipedia does have an extensive list. That said, some of the most common include:
- Affinity bias: A tendency to favour people most like us.
- Anchoring bias: An individual’s judgement or decision is influenced by information, or anchor, which could be completely irrelevant.
- Confirmation bias: Occurs when someone interprets and favours information which supports their beliefs and values.
- Contextual bias: This can occur when information about the context of an event or how it’s presented influences reasoning, despite the fact it’s logically irrelevant to the decision.
- Identifiable victim effect: Addresses how people can be more effectively influenced by a story rather than facts and evidence.
- Implicit bias: Assigning positive or negative qualities to a group of individuals. These biases can be nonfactual and reinforce stereotypes, generalisation and prejudice.
- Overconfidence effect: Where an individual overly believes their own decision-making skills.
There are many other cognitive biases. They offer fascinating insights into how we behave and think and can impact our everyday lives. Consider the spotlight effect, where you can overestimate how much time others think about you, and the status quo bias where people prefer things to remain as they are and become averse to change.
You’ll also find there are claims for more peculiar biases. Take for example the Interoceptive bias, more commonly known as the ‘hungry judge’ effect. A 2011 study published in the Proceedings of the National Academy of Sciences claimed judges were more lenient in their rulings after a break because they were fed and rested. Though it’s worth noting that this particular study has since been heavily criticised, for some it also demonstrates how biases could potentially arise without a person fully realising it.
Cognitive bias in legal proceedings
We’re all susceptible to cognitive biases and, unfortunately, there is data and research to suggest that these biases can have an impact on legal proceedings. Everyone in a courtroom from legal professionals to the public members of a jury can have cognitive biases.
Cognitive bias in juries
In research on cognitive bias the Parliamentary Office of Science and Technology (POST) reported that “attitudes about the workings of the justice system can influence the decisions that they make in studies designed to reflect a court case”. Research has found that a juror who feels the justice system is ‘too lenient’ may lean more strongly towards conviction than someone who doesn’t share such views. This provides an example of cognitive bias before a case has even seen the inside of a courtroom.
Under the Criminal Justice and Courts Act 2015 “It is an offence for a member of a jury at an inquest to research the case during the inquest period”. There are exceptions to this and, for the courts to find someone guilty, they must prove an individual was intentionally carrying out research. However, with news now so immediate we can be subjected to opinions, misinformation and disinformation by simply opening a social media app on our phone which could unintentionally inform decision making.
The POST report offers some insight into how the publicity of a case or trial can shape decision making. For example, “an analysis of 44 US-based studies revealed that negative pre-trial publicity significantly affects jurors’ decisions about the culpability of the defendant”. They also reference a Ministry of Justice report that found, in a sample of jurors, 70% serving on “longer, high profile cases” recalled media coverage of the case. 20% of those who recalled media coverage said they had found it difficult to disregard. They concluded that “less than half could identify whether the reports framed the defendant as innocent or guilty, but of those who did, almost all recalled the defendant being framed as guilty.”
Cognitive bias in legal professionals
Whilst legal professionals are potentially more aware of cognitive biases it doesn’t mean they’re free from falling victim to them. Tom Stafford, a Professor of Cognitive Science wrote in Tribunals, a journal for the Courts and Tribunals Judiciary Service, said: “We are all vulnerable to [cognitive biases], and they are difficult to account for, even if you know about them…even for judges.”
Though cognitive biases in legal proceedings are felt across social categories such as gender, class and sexuality, one area that seems to be particularly prevalent is racial bias.
Racial bias in the judiciary
Stafford’s article highlights a study of white American judges which found they showed “the same automatic, ‘implicit’, negative associations with race as found in the general population”.
A report into differential treatment in the youth justice system in the UK revealed similar prejudices. It found young black men almost seven times more likely to receive a sentence of 12 months or longer than young white men, and young men with parents of different ethnicities are 2.7 times more likely to be prosecuted than young white males. For young females with parents of different ethnicities the statistic was even more startling, with their chance of being prosecuted six times more likely than that of a white female who has committed a similar offence.
The Centre on the Dynamics of Ethnicity (CODE), the UK’s largest research centre working on racism, antiracism and racial, ethnic and religious inequalities, produced a report on judicial racial bias. The report found “95% of the legal-professional survey respondents said that racial bias plays some role in the processes and/or outcomes of the justice system, with 63% saying it plays a significant role, and 29% saying it plays a ‘fundamental role’”. It also reported that “racial discrimination by judges was most frequently directed towards Asian and Black people” and respondents identified people from Black communities as “by far the most common targets of judicial discrimination”.
Verbatim comments from those surveyed for the report also reveal a wider view of how social categories entwine and propagate cognitive bias. “I have seen judges (and magistrates) behaving in biased ways with people on a number of occasions. Because of the intersectionality between race, class and gender, it is difficult to say on what basis bias has been exercised.”
Anti bias strategies for legal professionals
The CODE report also highlighted examples of antiracism by judges, the proactive mitigation of racism, which showed “what can be done in courtrooms”. In his piece for the Tribunal, Stafford also offers advice on how the judiciary can combat cognitive bias: “We are often focused on the personal level – what can I do about bias, how can I avoid bias – but we should not forget that our work involves others, who will also have their own biases, and we can play an important role in addressing their biases, just as they can play a role in addressing ours”. As well as addressing personal biases and those of peers (which he states can be easier), Stafford also points to challenging biases present within the institutions we work to make fairness the norm.
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