With the ubiquity of camera phones, CCTVs, and the increasing trend of police officers wearing cameras when on duty, the use of video footage in the courtroom as evidence is rapidly becoming standard practice. But by slowing down the footage to make things easier for jurors to see, it may be having unintended consequences in the courtroom.

Researchers from the University of Chicago have found that by showing a jury a video of the crime only in slow motion, they were three times more likely to convict the defendant of first-degree murder. This could obviously have profound impacts on the justice system, if those making these decisions are being unintentionally influenced.

The study, published in the Proceedings of the National Academy of Sciences, conducted a series of mock trials using volunteers. They asked them to act as a jury, and then played them a clip of a violent crime recorded on CCTV in either real time or a slowed-down version. They found that those who were shown just the slow-motion version were 3.42 times more likely to reach a unanimous murder verdict, compared to those who were shown the regular clip. Not only that, but when the experiment was repeated with the time shown in the corner, allowing the jury to know how much time had elapsed, they were still more likely to be biased.

One of the key components of determining someone’s guilt for a violent crime or murder is whether or not there was intent in the action. The researchers suspect that by slowing down the footage, it gives the jurors a false sense that the defendant had more time to think and deliberate over the act, making them believe that there was more intent then there actually was at the time. This, they suggest, makes the jury more likely to convict. When the mock jury was shown both the regular clip and the slowed-down version, the effect was massively reduced, with them 1.5 times more likely to convict.

Interestingly, this effect might not just be confined to the courtroom. The use of slow-motion playback is now a staple in sports, particularly when a referee is deliberating on a punishment. While it may seem like that this would make sports fairer, it could be having the opposite effect. The researchers found that the longer time a referee had to deliberate over whether or not to punish a player, their bias against the player in question increased. Again, this is probably to do with the fact that with hindsight, the referee may think that the player should have behaved differently.