The lord chief justice has today warned of the need to preserve the integrity of the trial and jury system in the face of risks posed by modern technology.

In his foreword to the Court of Appeal Criminal Division’s annual review of the Legal Year, Lord Judge stressed: ‘Modern technology does not come without risks.’

He said: ‘I remain concerned at the ease with which a member of the jury can, by disobeying the judge’s instructions, discover material which purports to contain accurate information relevant to an individual case or an individual defendant.

‘I am also concerned that the use of technology enables those who are not members of the jury to communicate, in both directions.’

Judge warned: ‘In the context of current technology, we must be astute to preserve the integrity of jury trial and the jury system.’

Highlighting wider concerns about the integrity of the jury system, the annual report shows that in three separate appeals last year convictions were found to be unsafe in the light of jury irregularities - though none of those concerned use of technology. Retrials were ordered in two cases.

In two other cases the court endorsed decisions made in the Crown courts that trials should proceed without a jury, either because of the danger of jury tampering or where this had occurred.

The report revealed a 2% drop in the number of applications compared with 2009/10, to 6,972.

The majority of the court’s work concerns appeals against sentences. In the last year it received 5,481 applications to appeal sentences, down from 5,653.

In addition it received 1,491 applications to appeal convictions, roughly the same as 1,480 applications received in 2009/10.

During the legal year, which ran from October 2010 to September 2011, the Court of Appeal heard 535 full conviction appeals, up from 488, and 2,004 full sentence appeals, down from 2,136.

In addition it dealt with 1,251 applications for leave to appeal conviction and 4,039 applications for leave to appeal sentence.

The annual report shows that on average over the last three years, 13% of conviction applications and 26% of sentence applications received were successful.

On average appeals against conviction were dealt with in 9.3 months, while sentence appeals were disposed of in 4.6 months.

The attorney general referred 101 potentially unduly lenient sentences to the court, which resulted in increased sentences in 82 cases.

The annual report also noted that the Court of Appeal has continued to use technology to improve its efficiency and reduce costs, particularly through the use of video-link facilities.

Last year, it held 99 video-linked hearings to locations including 35 prisons and six courts. This meant appellants and witnesses were able to give evidence without having to attend at the Royal Courts of Justice.

In one case two vulnerable child witnesses were able to give evidence from their local magistrates’ court rather than having to travel to London.