In a discussion in my presence of a similar case a few months ago, someone (a man) said that it was no-one else's business what pictures someone had on their computer, and they should not be arrested for it.
I would not agree. I was scanning an online newspaper a few years ago, and saw a name which sounded familiar. A man had been convicted of possessing indecent photographs of children. The name was distinctive, so I Googled it to find out more. Turned out he was a music teacher, taking classes part-time in several schools and giving private one-to-one lessons in pupils' homes, and organising musical events. He also sang in a prominent choir which was mostly composed of children aged from 7 to 14, who had rehearsals every morning before school, and every afternoon after lessons, and sang at two Sunday services and one midweek one, with rehearsals before each service. Plenty of opportunity to make "friends"
This man was in contact with young children from early morning until late evening, hundreds of them, in schools, churches, and private homes, often alone and close up. If he had not been charged and his trial and conviction reported in the press, who knows what harm he could have done?
It would not have been publicised that someone with that kind of interest was working and socialising with children if he had not been breaking the law by owning the photos.