Addressing Judge Mark Callaghan on the second day of the trial of Vaughan Grosvenor Mabee (26) on Friday, Allan Tobeck said police should not have been in the hospital room when the sample was taken from Mabee, who had suspected concussion from the crash.
``When police are present when a doctor is examining a patient who is a suspect, their presence is an influence in what the doctor says to a patient and can result in a misdiagnosis.''
There were ``competing interests'' between police gathering evidence and medical staff assisting an injured person, he said.
Mabee, of Ben Lomond, denied charges of drink-driving and careless driving in relation to the 2013 incident, in which his heavily damaged, bloodied Toyota Hilux was found empty in a ditch beside Arrowtown-Lake Hayes Rd about 12.50am on November 14.
Police eventually found Mabee at his employer John Darby's house at 2.16am.
After a breath screening test gave a reading of more than 400mcg, they took him to Lakes District Hospital for assessment for a suspected head injury.
A blood sample taken at 3.45am gave a reading of 137mg.
Called by the Crown to give evidence, Mabee's wife, Anne Schneeberger, said she did not pick up her husband from Mr Darby's house because she was on antibiotics, had a migraine and was feeling ``loopy''.
After speaking to her husband on the phone, she was convinced by his explanation that a stray dog and bald tyres had caused the crash rather than alcohol.
``What I'm sure of is that he was completely sober.''
She did not realise how serious the crash was until later.
Judge Callaghan set a schedule for the Crown and defence to provide written submissions, and reserved his decision until March 7.
