He subsequently claimed ACC payments and in May 2000 ACC also approved attendant care payments to Mrs Brennan for seven hours per day, five a days a week.
Between December 1999 and September 2011 Mr Brennan received ACC payments totalling $665,696.89 gross, and his wife received $55,790 in attendant care payments between 2000 and 2003.
The Crown's case was that a few months after Mr Brennan was assaulted he resumed working in his workshop, building engines and carrying out work on various vehicles for customers. This was evidenced by the labour content of various invoices.
However, during interviews with ACC staff, occupational therapists, medical and health assessors Mr Brennan would present as severely impaired.
In 2003 Mr Brennan resumed his high-performance motor sport racing activities, and went on to compete in various race meetings, including winning one in Thailand in 2010.
The Brennans argued they believed that until Mr Brennan was back to the same work skills and abilities he had pre-assault, then they were entitled to compensation and attendant care payments.
In Judge Marshall's written judgement released to the Bay of Plenty Times, he outlined his reasons for the guilty verdict.
He said after hearing from numerous witnesses including past and present customers of the Brennans, he was satisfied the Crown had proved all the charges beyond reasonable doubt.
Judge Marshall said the Brennans actions were clearly intended to deliberately deceive ACC and medical and health professionals into believing he could not do any productive work.
"Once Mr and Mrs Brennan embarked on this course of deception they could not disengage from it. They seemed to be compelled to maintain this deception, which standing back and viewing the evidence as a whole, overwhelmingly discloses the dishonest actions of Mr and Mrs Brennan.
"I find on the evidence that the attendant care provided by Mrs Brennan was an elaborate scam for them to obtain more money from ACC."
Judge Marshall remanded the Brennans on bail pending sentencing on February 22, and ordered them to surrender their passports.
Outside court Paul Mabey QC declined to comment, and said it would not be appropriate for his clients to comment on the verdict ahead of sentencing.
ACC spokesperson Stephanie Melville said: "New Zealanders pay ACC levies to help those with genuine injury-related needs and we are committed to ensuring that this money is used for its intended purpose. ACC is satisfied with the decision."