Evidence to be presented to the jury would include CCTV footage showing smoke coming out of the top of the roller door shortly after Harrison left the shed and drove away.
Later he told a fire investigator he didn't think the security cameras at the property were working, Barnaart said.
Neighbours saw the smoke about 10 minutes later and called 111 after a failed attempt to douse the flames with a garden hose.
Barnaart said the jury would also hear from two fire investigators, both of whom found the fire was deliberately lit using an incendiary in two places.
Other evidence would include that Harrison's wife and son made inquiries about insurance after the fire although no claim had been lodged.
Defence lawyer Michael Dodds said, however, there was ''no rhyme or reason'' behind the Crown's case and no sensible motive for Harrison to start the fire.
Harrison had no involvement in the building's insurance — that was controlled by his son, who co-owned the Waipapa Rd property — and the household contents were uninsured.
Those contents included heirlooms from his late mother, musical instruments, and his wife and child's personal belongings.
The shed's business contents were insured but Harrison had lodged no claim so he could not benefit from the fire as the Crown alleged, Dodds said.
''This was a tragedy of huge proportions that destroyed 35 years of hard work ... However the fire started, it wasn't lit by the defendant.''
Yesterday the jury also heard from neighbours, a friend who had visited the property earlier that day, Harrison's sister and police.
Today they will hear from fire investigators and a number of technical experts.
The trial is expected to run until Thursday next week.
