How do you know he was the one doing the clicking?
Was there illegal child porn on his computer?
How do you know he was the one downloading child porn, if there was any?
Here’s the deal. There isn’t a shortage of perverts on the web and they are VERY VERY stupid. A friend of mine hunts them for the State Police in another state. They are self-documenting. If they are downloading child porn, they will provide the evidence to convict them.
There are so many easy targets, the cops don’t waste time with “possibles”. If you “accidenally” click on it, they aren’t going to kick down your door.