Research from a team of academics has found, unsurprisingly, that attitudes held by jurors colour their understanding of the concept of reasonable doubt and have a ‘significant’ impact on the verdict they are likely to deliver.

Given the restrictions on jury research, a group of employees at a pharmaceutical company in Cambridge was asked to consider a ficticious burglary case.

The research subjects completed a questionnaire based on 29 statements designed to judge their ‘conviction proneness’, cynicism toward the defence, racial bias, and their attitudes toward social justice and 'innate criminality'.

Those who agreed with statements exhibiting conviction proneness and cynicism towards the defence, such as:

•    Criminals should be caught and convicted by any means necessary;
•    In most cases where the accused presents a strong defence, it is only because of a good lawyer;
•    Defence lawyers don’t really care about guilt or innocence, they are just in business to make money;
•    Defence lawyers are too willing to defend individuals they know are guilty; and
•    Lawyers will do whatever it takes to win a case.

were more likely to have a pro-prosecution stance and required a lower threshold to find someone guilty.

Those who rated their responses to the same statements lower and had a more pro-defence outlook were likely to have a higher threshold for the burden of proof before convicting.

This may sound obvious, but it is still worth stating – the fact that extra-evidential factors affect jurors’ decisions should be acknowledged.

Jurors cannot leave their characters, preconceptions and prejudices in the retiring room with their coats, but bring all of their characteristics and experience of the world into the court.

And it is with those characteristics and experience that they assess the evidence and the veracity of witnesses – that’s the point of them.

The research also found that many of the sample did not understand properly the standard of proof, despite being given a sample judge’s commentary, raising the possibility that the concept could be applied inappropriately.

These two factors should not undermine the principle of the jury system. The way the system works was vindicated in 2010 research by Professor Cheryl Thomas of UCL, which showed that juries are fair and do not discriminate on grounds of ethnicity.

What Thomas’s and the recent study by Samantha Lundrigan and others show is that jurors perhaps need greater guidance on the interpretation of legal concepts – particularly the burden of proof.

Research into juror behaviour is fascinating, yet at the same time tantalising – as actual jurors cannot be asked about how they reached decisions.

As we learn more about how juries work, are we edging closer to the day when the sanctity of the jury room is burst open? And if that day comes, will we like what we find?

Catherine Baksi is a Gazette reporter