Mr Dixon said Mr McKinnell told police during a search of his Mount Lawley property in May 2016 that he searched for "normal porn" and sometimes female teenagers.

"He said, 'yeah, you'll find lots of porn on there but it's nothing questionable, anything I've opened up that's a bit iffy I've deleted straight away'," he said.

The court heard Mr McKinnell had more than 200,000 pornographic files stored on his laptop, with the images in questions making up around 1.5 per cent of the material.

He claimed while downloading multiple pornography files at a time, any suspicious images which could be child pornography he would place in a sub-folder labelled SPEC to review later and delete if he believed an image was "dodgy".

Mr Dixon said a police data analysis expert, however, would give evidence during the trial which would allege Mr McKinnell very rarely deleted images from his laptop.

"Of the 3,009 pictures the state alleges are child exploitation material, only 15 were located in the folder the accused referred to in police interviews as SPEC," he said.

"It appears... that there were only three days over a two year period where files were deleted from the computer... [the data expert] did not detect any files to be deleted from that [SPEC] folder."

Mr Dixon said of the 3,009 images the state alleges were child pornography, the majority showed girls who were prepubescent, reaching or on the cusp of puberty.

"It will be very clear to you that these girls are prepubescent," he said.

Under law, a person cannot be found guilty of possessing child pornography if it comes into their possession unsolicitated and the person then removes it from their possession.

Defence lawyer Anthony Elliott urged the jury to remain open minded while hearing the evidence, despite some people viewing pornography as a "revolting thing".

"[Mr McKinnell] was a man that endeavoured to delete any pornography that was illegal," he said.

A video of the police search of Mr McKinnell's home showed the teacher assisting child abuse squad detectives to inspect his property and laptop.

He told police during the search, "I just want to get this cleared up and get my computer back for work".

Asked if he had any valuables in the house he joked, "No, I'm a teacher".