A Supreme Court justice today told experts that they must avoid the risk of taking sides and advocating for their instructing party. Lord Hamblen told the Expert Witness Institute that cases where experts were admonished for being partisan by the court had occurred ‘far too often’ in recent years – each time to the detriment of those they speak for.

Hamblen said witnesses should refrain from becoming an advocate themselves and give evidence in such a way that you would not know which side has instructed them. ’There is nothing more fatal to the acceptability of an expert’s evidence than the questions of independence and impartiality,’ he said. ‘It will taint all [and] it is therefore vital to avoid any hint of partiality.

‘It is counsel’s job to argue a case – that is not the role of an expert. If you give evidence in an argumentative manner that will undermine your independence. Never get into an argument with counsel however provoked you might be.’

Hamblen said there had also been cases in the High Court where 'experts' appeared without having specialist expertise in that particular field, adding: ‘It is not the experience of giving evidence in court that makes you an expert.’

His words were endorsed during a panel session of judges working in the civil and criminal courts. Senior Master Fontaine said there was concern that witnesses losing their impartiality might cause relevant evidence to be left out of reports. She told experts to reject any attempts from solicitors to put the case more strongly and added: ‘Don’t allow your enthusiasm to assist your client to cross the threshold into an unacceptably partisan approach.'

Recorder Simon Jackson also expressed concern about experts being ‘paid by results’ which was not consistent with their duties to the court.

Meanwhile, Her Honour Judge Sarah Munro warned against experts instructed in criminal courts from speaking in complex or technical language. She added: ‘Ensure the expert speaks to their audience. In my sphere that is a jury of 12 people, and an expert really needs to pare down what they are saying and make it very easy to understand – sometimes experts are inclined to show off their knowledge and complicate [matters] rather than helping the jury.’