Is there anything at all that gives you reason to beleve he has viewed under-age porn (ie sex or nudity involving persons below the age of consent, not 18, 19 year olds)
The laws in Oz might be different from elsewhere, but in order for an image of a naked child to be considered to be child pornography there generally needs to be a depiction of certain orifaces or sexual activity itself. Videos of nudists engaged in non-sexual activities, including children, are (again, generally) not considered to be pornography - even if it is clear the people who enjoy looking at naked children may have some agenda other than art appreciation. All of which to say, be careful about the legal aspect of things, because they can backfire on you. But the man's wife will not be swayed by legal hair-splitting, if you really want to take this guy out and you think you can successfully expose him with evidence.
In your place, I would go for the juglar, but that's just me.