'Seven jurors better than 12 for agreeing a verdict'

Seven jurors would be more likely to agree on a verdict than the traditional 12, researchers say.

A study of the psychological effect of group dynamics suggests there would be fewer hung juries if they were made smaller.

The research found that in a small group people share views, while in larger groups people become dominated by one or two individuals - making it harder to achieve consensus.

The research at Glasgow University showed a psychological switch flipped after the group grew larger than about seven or eight individuals. Then, people became dominated by one or two individuals who influenced the others.

This made it harder for a jury to achieve consensus. Members of the jury tended to gravitate towards one dominant individual or another.

Professor Simon Garrod conducted the research with groups of five and 10 university students asked to consider a case of plagiarism.

At the British Association science festival at Glasgow University, he said: "We found that the size of the group had a big impact. In small groups of seven or less you get a communication process, involving face to face dialogue, ideal for establishing consensus.

"In large groups everybody's very much affected by the dominant speakers, and they're not influenced by the people they are sitting next to.

"This might explain why large juries tend to end up with hung decisions. From the point of view of establishing consensus, 12 is not the optimum number for a jury."

He said in small groups the dominant individuals actually say more - but what they say makes less impact.