A string of ACT Supreme Court juries in unrelated trials have been unable to reach unanimous verdicts in recent weeks.

Since September 18 only one jury has been able to agree on a verdict, taking less than three hours to acquit a man of sexually assaulting a teenager on school ground.

But four out of five juries found themselves hopelessly deadlocked, forcing a judge to send them home.

For victims, defendants, their families and lawyers it's a frustrating and costly outcome, and can mean a lengthy wait for a retrial.

The reasons for the spate of deadlocked cases remain shrouded in the secrecy that surrounds the jury room and the deliberations within its walls.

Yesterday, Jeremy Scott Campbell became the fourth accused man to face the prospect of a retrial after 12 men and women could not agree on his drug trafficking charges.

Campbell had been accused of dealing ice and methylamphetamine but after nine hours the jury wrote to Justice John Burns asking to be sent home.

The prospect of a retrial frustrated his sister, a defence witness, who supported her brother throughout the process.

''It's wasting taxpayers' money, it's wasting families' money,'' she said. ''I understand it happens, that they can't decide, but it should be the option of the judge, not to have to wait another year or two to do the whole thing over again.''

In several jurisdictions judges can accept majority verdicts, but ACT Law Society president Noor Blumer warned against such a move.

She noted recent amendments ruled out judge-alone trials for people accused of homicides or sexual assault offences.

''There is no such thing as a hung jury when there is only a judge,'' Ms Blumer said.

''Having lost the option of a judge-alone trial except in exceptional circumstances, it would be grossly unfair if defendants were then subject to majority verdicts.

''The justice in the jury system is that if even one of the jurors has a 'reasonable doubt' then there is no conviction.''

The three other deadlocks all came in cases involving sexual assaults.

Earlier this month a jury was sent home after failing to agree in the case of a masseur accused of sexually assaulting a customer on a massage table. The man's barrister, James Lawton, said his client now had a tentative December 2013 retrial date.

''[Hung juries are] extremely stressful for the accused, and because of the delays in getting things relisted the matter won't get heard again until as late as next year,'' Mr Lawton said.

''That often means complying with bail conditions for an extended period of time, being unable to move on with their lives.''

The former prosecutor also said the Director of Public Prosecutions had to carefully consider whether to mount a retrial.

''The director has a two-part test to apply before deciding to prosecute - whether it's in the public interest and whether there are reasonable prospects of conviction,'' he said.

''A hung jury may well demonstrate there aren't reasonable prospects.''