The former head of road policing for Grampian was unfairly interviewed by colleagues over a driving charge, a sheriff has ruled.
Ch Insp Tom Forrester and Pc Ashley Forbes deny dangerous driving.
The vehicle they were travelling in was involved in a collision on the way to Aberdeen Airport in 2008.
Sheriff Kenneth Stewart said an interview in which Mr Forrester was questioned without a lawyer was unfair and ruled some evidence inadmissible.
Pc Forbes was driving Ch Insp Forrester to Aberdeen Airport when their vehicle was in a collision on the B977 Dyce to Belhelvie road.
The trial has heard how Ch Insp Forrester and another colleague, Insp James Wood, were running late for a flight to Birmingham to attend a conference.
The trial, at Aberdeen Sheriff Court, will resume on Thursday when a decision on no case to answer submissions is expected to be made.