Senior police officers joked about framing Arthur Allan Thomas for the Crewe murders while drinking at a bar, says a woman who worked there.
Queenie Edmonds said she overheard the talk while working at the Mangere Hotel 43 years ago at the time of the investigation.
Ms Edmonds told One News that she heard police officers, including Bruce Hutton, who led the investigation, call Thomas a "half-wit".
She said police had bragged they could get away with anything.
"I thought it was idiocy that they could do that to another human being," Ms Edmonds said.