The fire investigator who examined the scene of the Wastebusters Alexandra recycling centre blaze did not use proper scientific methods, the Dunedin District Court heard yesterday.
Aaron Gourlay (43) denies having set fire to the property, which burnt down on September 3, 2015.
He also denies arson charges relating to three motor vehicles and intentional damage charges relating to two other vehicles.
Yesterday, Australian fire consultant Ross Brogan, the sole witness for the defence, said Catherine Trevathan - the specialist fire investigator who conducted the scene examination the day after the Wastebusters fire - had not eliminated all possible causes of the blaze before deciding it was suspicious.
Mr Brogan also questioned whether Ms Trevathan was qualified to conduct a scene examination, as she was yet to complete her final paper in an Australian course conferring a qualification in fire investigation.
Responding to questioning by defence counsel Adriana Pinnock, Mr Brogan said Ms Trevathan did not follow appropriate scientific methods to eliminate potential causes of the fire such as rodent damage to wiring, or an electrical fault.
He also felt she did not properly address what caused two holes in the floor of a portable building used by Wastebusters as an office.
Mr Brogan said Ms Trevathan's notes mentioned electrical issues, but did not conclusively rule it out as a possible source of the fire.
Similarly, her notes said ``always rats'' but then did not explore whether rodents could have played a part in the fire igniting.
``It wasn't asked, it wasn't explored, and there are no notes taken that show it was explored and eliminated.''
With no evidence what had started the fire, its cause should have been classed as ``undetermined'' rather than suspicious, Mr Brogan said.
In cross-examination, Crown counsel Craig Power took Mr Brogan through several findings Ms Trevathan had made about the fire, most of which Mr Brogan agreed with.
When asked if it was an extraordinary coincidence a tyre with petrol inside it should be on the Wastebusters site the day an electrical fault might have occurred, Mr Brogan said investigations had not shown conclusively what ignited the fire.
Mr Power also noted the paper Ms Trevathan was missing for her fire investigation qualification was on fatal fires, and the Alexandra Wastebusters fire had not been a fatal fire.
The defence concluded its case yesterday.
Today the jury will hear closing statements from the Crown and defence and the summing up of Judge Kevin Phillips before retiring to consider its verdict.
