Harvey and Jeannette Crewe were shot dead at Pukekawa in 1970.
Mr Thomas, a local farmer, was convicted at two trials of murdering the couple before being pardoned. A royal commission later named Mr Hutton and another officer as responsible for planting the bullets that led to the convictions. Police unsuccessfully challenged the finding.
The case is the subject of a police review after the daughter of the murdered couple asked Prime Minister John Key to help find her parents' killer. The findings of the two-year review are expected to be released soon.