Police and prosecution lawyers called in the Security Intelligence Service to check if their offices were bugged during the 1980 Royal Commission into the Thomas case.
Former detective Stan Keith remembers the SIS regularly sweeping the police room where Crown solicitors worked, searching for listening devices.
"Police had concerns during the hearings that their discussions about the case might be monitored," Keith told the Weekend Herald. "They were worried their conversations would have been used by the commission."
Although the SIS never found anything, the incident summed up the atmosphere of intense mistrust on both sides.
Defence lawyers and Thomas supporters had accused the police of a series of dirty tricks, from the original planting of the shellcase which convicted Thomas to stacking juries and bugging the defence's phone calls.
The police believed the Commission, led by outspoken Australian judge Justice Robert Taylor, was out to get them. They regarded the hearings as a trap set by Prime Minister Robert Muldoon, who had taken a strong personal interest in the case and become convinced that Thomas was innocent.
The result confirmed all the Thomas camp's hopes and the police's worst fears. The commission directly accused Detective Inspector Bruce Hutton and Detective Len Johnston (who had died two years earlier) of planting the shellcase to frame Thomas and described his imprisonment on false evidence as "an unspeakable outrage".
Today Hutton admits that the aftermath caused some strain in his personal life but adds, "I didn't lose any sleep at any stage."
The 81-year-old, who lives in retirement in South Auckland, says he has no regrets about the case, apart from the Royal Commission's findings. "I just feel the way it was handled was very unfair to the Crown, the police and me - and Len Johnston in particular."
He feels vindicated by a Solicitor-General's report to police that the evidence did not justify laying charges against him.
Hutton can still tell stories of support from high-profile New Zealanders, who have since died. Former Federation of Labour president Sir Tom Skinner tipped him off about Thomas' pardon in a restaurant, saying Prime Minister Robert Muldoon had let slip that it was in the pipeline.
He says former Governor-General Sir David Beattie - who used to be a lawyer in the Auckland courts when Hutton was a police prosecutor - once took him aside in the president's room at the Trentham racecourse and said: "Bruce, I just want you to know that having to sign that pardon for Thomas was the hardest thing I've ever had to do in my life. I just want you to know that Muldoon insisted."
Unhappy at being transferred from the CIB to the uniformed branch, Hutton retired from the police in 1976. He's adamant his decision to leave was not influenced by the Crewe murder case.
"I always said I wasn't there for the long haul, that I wanted to go back farming and have a go at breeding horses."
After Hutton's retirement, Keith took over as "minder" of the 29 boxes of Crewe murder files held in Police National Headquarters archives. He has made countless trips to Wellington to answer queries for information.
"It has been my life," said the 69-year-old, who retired from the police with the rank of detective inspector in 1995. "If it hadn't been for this inquiry, I would have chased promotion within the police.
"You get politicians, you get ghouls, you get journalists who want to write books and you get those who want to make films. You get heaps and heaps of correspondence that comes through from headquarters.
"I've had enough of it and I've told them so."
Lawyer Peter Williams, who represented Thomas at the Commission, has little sympathy for the police complaint that Muldoon overrode the whole legal system - "the judicial process hadn't really helped Thomas very much" - but agrees that his personal intervention was crucial.
"Muldoon read the file, which was quite extraordinary for a politician. He sat down with us at the Intercontinental Hotel and he discussed it with us at length. I'm talking about hours of discussion and he had an amazing knowledge of detail."
He remembers Hutton giving evidence to Justice Taylor at the commission. "They had the court packed with police and they booed Taylor because he was so direct in his questions. I've never seen anything like it in my life.
"There are still officers today who say Thomas was guilty. It was a classic case of tunnel vision."