The Law Society says the public will have to put up with longer delays in getting to court and judges will be under more pressure as the Criminal Procedure Act beds in.
Chief District Court Judge Jan-Marie Doogue says that for a period in the middle next year, there will not be enough judges to hear cases.
Judge Doogue estimates the shortfall in judges will peak in the middle of next year and says she is working with senior judges to ensure there is no undue delay in serving the community's justice needs.
The convener of the Law Society's criminal-law subcommittee, Jonathan Krebs, says the Criminal Procedure Act has caused judges to spend more time writing up judgements and less time in court.
He says that makes for longer delays in getting cases heard, which may lead to miscarriages of justice.
"It'll be a matter of time before the question of delay becomes an interests of justice question, where witnesses have died or moved away or for whatever reason are unavailable and justice can't be done and so a case will be stayed - and that can't be good for our community."
The Criminal Bar Association's vice-president, Noel Sainsbury says the new system is being propped up by the will of everyone in the court system to make it work.
But Mr Sainsbury says if those in the court system let it collapse, the Ministry of Justice might get the message it is under-resourced.