Defence lawyers have questioned Justice Minister Simon Power's claims that a revamped criminal justice system would save more than 1100 cases from being committed to jury trial each year - a saving of $20 million.
In May, Mr Power proposed that anyone facing charges punishable by less than three years
in prison should be able to be tried by a judge alone.
At present, those facing sentences of three months or more can choose a jury trial.
Such a radical change may require amending the Bill of Rights, but Mr Power said the reform - with "changes to the prosecution's discretion to lay charges" - would save around 1100 jury trials each year.
However, Justice Ministry figures provided to the Criminal Bar Association under the Official Information Act show that the proposed changes to three-month threshold would have saved 184 trials in 2007.
The estimate of 1100 jury trials came from combining the 184 figure with removing the ability of the prosecution to choose the form of trial - whether charges were laid summarily or indictably. The number of fewer cases committed to trial would have been 966, according to the 2007 figures.
"As approximately one-third of committed cases are matters where a verdict was reached, we have estimated that, from these 1100 fewer cases being committed to trial, 300 jury trials could be saved," the Justice Ministry said.
There were 1417 jury trials held last year, of which only 136 related solely to charges where the maximum penalty was three years or less. Of the 264 jury trials in the Auckland District Court, only 21 was in that category.
The proposal to lift the jury trial threshold from three months to three years has outraged defence lawyers, who say that would affect a defendant's right to a fair trial.
When questioned about the figures, Mr Power told the Weekend Herald he had "always made it clear" that the 1100 figure was estimated from combining the two factors.
