A forensic pathologist is warning the country is on the brink of a "catastrophic unravelling" of the service.
Dr Martin Sage said by June the pressure would be so great on the country's handful of forensic pathologists that some autopsies would not get done and inquests would be put off.
The crisis could also have an impact on evidence for murder and other serious criminal trials.
RNZ News asked Dr Sage, of Christchurch, about a defence lawyer who faced a problem getting a forensic pathologist's report for a trial in Rotorua.
"[You] can't divide off the idea of people advising defence from the resources available overall in the country in forensic pathology, which is currently on the brink of a major catastrophic unravelling of the service.
"Within the next couple of months there are going to be major issues in various parts of the country.
"This underpins the difficulty that defence counsel might then have in obtaining expert advice."
He would not say which regions would be hit first. The chief coroner had been briefed, though Dr Sage would not say by who.
Dr Sage described a situation where only the equivalent of 6.5 forensic pathologists cover the whole country, but one of those was retiring before June.
Inquests could be cancelled before the end of June and, asked if the timeframe for inquests could just be pushed out, he said, "Well, you can't just keep bodies stacking up, it doesn't work like that."
Dr Sage laid the blame on the Justice Ministry for what he called a high-risk and highly uncertain funding system, and its refusal to enter into a decent contract with the Auckland District Health Board.
The DHB's forensic leader would not talk to RNZ News. But Ministry of Justice senior manager Heather Baggott said in a statement the forensic pathology service was sustainable and stable and working well.
The ministry had recently been made aware the number of pathologists covering the Auckland region might drop in coming months and the Auckland DHB was working to fill vacancies, but there were no vacancies in other regions.
The ministry and DHB were working on extending the current contract.
The chief coroner, judge Deborah Marshall, declined to be interviewed.
Defence lawyer turned to UK pathologist
The signs of pressure are already there for a defence lawyer representing two people facing charges over the death of a three-year-old Taupo boy last August.
Andrew Schulze said he had to arrange to use a forensic pathologist in the UK to review the Crown's evidence, at a cost of about $5000, after being turned down by three pathologists in New Zealand, including Dr Sage who was too busy to help.
"The hurdles that defence have to cross to obtain and retain the services of an expert - it's a live issue for all defence counsel I would have thought," said Mr Schulze.
"It's a matter of resourcing really, and I don't know whether, given the size of the country and the resources that we have, that that's a matter that can be solved with the stroke of ... granting more money."
He was waiting to hear whether he would get legal aid to cover the cost, but expected the trial would be able to go ahead as scheduled in early May.
Homicide and other court cases account for only 10 percent or so of forensic pathologists' work, though Dr Sage said police and Crown Law needed to know about the crisis.
The contract his colleagues work under at Auckland DHB prevents them speaking out, but he is able to because he is on different terms.
He has chosen to speak now after a year of 50 to 60 hour weeks, carrying 1.6 times the internationally recommended number of caseloads.
"People are no longer prepared to continue to stretch further to fill the gaps, particularly in a situation in which we're being put into conditions which are hazardous both for us in personal health and safety, and hazardous professionally because if you try and do too much, that's when you drop the ball."
The crisis was putting off new people who could ease the pressure, he said. Also, forensic pathologists overseas were aware of the insecure contract and relatively low pay their colleagues in New Zealand worked under.