There are concerns Covid-19 patients may not always tell the truth about who they've been in contact with.
The issue was raised in discussions between senior Health Minister staff members about a report into three public health units' contact tracing ability carried out by consultants Allen and Clarke.
The "deep-dive" into the operations of Auckland, Hawke's Bay and Southern public health units between 20-24 April, found a reliance on manual processes and a lack of communication between units and the National Contract Tracing Centre.
However, the use of standardised scripts to try and ascertain close contacts and where they had been is cited as a potential concern by at least one senior Health Ministry staff member, according to emails released to RNZ under the Official Information Act.
"It is noted that using scripted approaches can potentially have the effect of limiting responses, and runs the risk of a tick the boxes-type response in some situations," the former detective wrote.
He recommended contact tracing staff be trained in "recall investigative interviewing" used by police if some patients were reluctant to reveal who they were with, or where they might have been.
"There may be a myriad of reasons for a subject to be less than truthful about contact with others if diagnosed positive for Covid-19."
Hawke's Bay and Auckland Regional public health units had identified a "reluctance among some" especially if they had been involved in a criminal activity, he said.
"Public health staff identified this was an issue in smaller communities due to shame/bullying."
Distrust of government agencies, general embarrassment or involvement in unauthorised activities could lead people to lie about who they had been with, he said.
"[There is a] real need to explore and deal with those types of issues from a public health standpoint during a pandemic."
However, the Ministry of Health said public health staff were well trained in interviewing and the scripts were only used as a guide.
"Our experience shows that in general people are open about their movements with the support of the skilled interviewers," A Health Ministry spokesperson said.
Further training in police-style interviewing was not recommended, they said.
"An enforcement approach to corroboration may have unforeseen and negative impacts such as losing the willingness of cases to comply with restrictions and requirements placed on them."
A veteran public health nurse from Hawke's Bay District Health Board and Contact Tracing Assurance Committee member Liz Read agreed.
In her years of dealing with outbreaks of communicable diseases she rarely had a patient try and hide information, she said.
"Generally, they are concerned about their friends and their family members and want other people to get tested. It's pretty rare to have instances of people not being honest with us."
All public health units had been building their contact tracing capacity and skills over the last three months, including participating in exercises to ensure they were ready in the event of another outbreak of Covid-19 in New Zealand.
"We hope all this work is a waste of time of course ... but there's a lot of work happening behind the scenes to absolutely make sure we have that surge capacity," she said.