Parkinson’s Disease Caused Child Porn Habit

Quoted:

A former headmaster who had thousands of indecent images of children on his computer walked free from court after a judge ruled the drug he had taken to treat his Parkinson’s disease was responsible for his crime.

I don’t understand. The issue of this case is “porn, hyper sexuality”? Or “child porn”? The drugs taken has caused him to be hyper sexually active. But he can, by all means, go into adult porn, right? Why child porn then?

Parkinson’s caused teacher’s child porn habit, judge rules