A woman who collapsed and died while giving an alcohol breath test to police in a booze bus was so stressed by the situation it set off an arrhythmia in her heart, a coroner's inquest has heard.
Coupled with an underlying heart condition, the arrhythmia appears to have overcome Elizabeth Jill Gilbertson, who died despite resuscitation attempts by ambulance officers called to the scene.
The 56-year-old was stopped at a police checkpoint in Hamilton on June 3 last year where she was found to have alcohol on her breath.
But when she failed several times to give a breath test Constable Anthony McFarlane escorted her to the booze bus on Cambridge Rd.
There she failed several more attempts which Mr McFarlane said he put down to nervousness.
Moments later she collapsed and "slid off" the chair, hitting her head on another seat as she fell to the floor.
Mr McFarlane called his colleagues for help and an ambulance was requested but before it could arrive, six minutes later, Ms Gilbertson's lips had turned blue, her face went pale and her pulse became faint.
Ambulance staff spent 37 minutes trying to resuscitate the South African immigrant.
At the inquest in the Hamilton District Court this morning, forensic pathologist Dr Simon Stables said he believed Ms Gilbertson suffered from heart disease.
"I think it is sufficient in the circumstances, especially coupled with the extreme stress, that this has been enough to tip the balance where she has suffered quite significant arrhythmic heart rhythm problem, and that's led to her death."
Dr Stables said Ms Gilbertson's heart problems, including enlarged heart muscle requiring more oxygen and a borderline severely narrowed coronary artery, meant when her heart went into arrhythmia she couldn't get enough oxygen.
"When someone is stressed their heart rate goes up, their blood pressure goes up, the heart starts beating faster, demands more oxygen."
A post mortem later showed Ms Gilbertson was well below the legal alcohol driving limit.
Coroner Gordon Matenga reserved his decision, which is expected later today or tomorrow.