Two members of the tiny Pacific Island community of Pitcairn Island took just 45 minutes to find their former mayor had indecent material in his possession.
Two assessors - effectively a mini-jury - selected from its community of about 50 people agreed that an internet sex chat with a person purporting to be a 15-year-old school girl and a video of a bound, gagged naked woman were grossly indecent.
Judge Arthur Tompkins, who issued his finding separately, agreed with that verdict and convicted Warren of the two charges.
Warren will be sentenced on Saturday on those charges, and 20 others relating to child sex photos and videos found on his computer, hard drives and CDs.
Judge Tompkins told the assessors they represented the right-minded members of the Pitcairn community and it was their job to determine what was and was not grossly obscene.
He reminded them the Crown's case was that the chat encouraged a 15 year-old to carry out depraved actions.
The defence's case was the chat was only a collection of words and Warren was not charged with the actions.
The two islanders, acting as assessors, walked across the Adamstown square to the island secretary's office and discussed the charges.
They did not take long to return findings that both items were indecent.
As well as being sentenced for the latest charges, Warren has also been convicted of a further 20 charges relating to hundreds of child sex images and videos.
During the trial, Crown prosecutor Kieran Raftery referred to historic child sex abuse trials that took place in 2004. In those cases, eight men were jailed for rape and sex abuse that had occurred on the island.
The assessors had a chance, 11 years later, to tell the world what was acceptable behaviour on the island, he said.
Warren's lawyer Graeme Edgeler argued there was nothing indecent about the online chat or the video.
The video was made with professional actors who had agreed to take part and put it on the internet, he said - and the online sex chat was so bizarre that it could not be real and was ridiculous.
The trial took place under the law of Pitcairn Island, which is a British territory about 540km east of French Polynesia.