SCOTLAND’S controversial not proven verdict should be retained because it does not affect the number of guilty verdicts and is not incompatible with the European Convention on Human Rights.

Those are two of the conclusions of Dr Lee John Curley of Edinburgh Napier University following a research project on Scots law.

Curley told The Conversation: “For this experiment we recruited 128 participants, and each participant acted as a juror in two separate mock murder trials.

“In one trial, the jurors could give one of three verdicts: guilty, not guilty or not proven. In another, jurors could give one of two verdicts: guilty or not guilty. Participants were also asked to state the likelihood of the defendant’s guilt after each piece of evidence.”

The research concluded that jurors were “significantly less likely” to give a not guilty verdict in the three-verdict system compared with the two-verdict system. There were also fewer not guilty verdicts than not proven verdicts in the three-verdict system.

Curley said: “Interestingly, there were no significant differences in relation to the number of guilty verdicts given across each of system; similar results have been found by researchers in the past.

“So if there wasn’t a significant decrease in guilty verdicts across the systems, then neither was there a significant increase in obtaining the acquittal verdict. The results showed that jurors did not give significantly different estimates of guilt across each system.”

He added: “The jurors presumed the same level of innocence about defendants regardless of how many verdicts were available, thus confirming that the not proven verdict does not undermine the presumption of innocence principle.

“This means that the Scottish three-verdict system is in line with Article 6 of the European Convention on Human Rights.”

Curley concluded by saying he “would recommend that the Scottish government retain the not proven verdict.”