In their defense, the psychotic killer was no more dangerous than fair rides, carnies, or deep fried Snicker's bars, so it's not like it increased the risk of harm that much.
further in their defense, apparently he was deemed safe enough to live free (albeit monitored) in society just the year before, and seemingly several times prior to that; according to the first article: "Phillip Paul has been on and off a variety of medications over the years, and also been in and out of institutions, Tom Paul said. He has repeatedly proven unable to live in society, he said.
Paul was living in a halfway house in Spokane last year, but ended up back at the hospital in a very agitated state, Tom Paul said." unless he'd wandered away from his halfway house or had dropped acid, freaked out, and hijacked a school bus full of penguins prior to getting himself re-institutionalized, I don't know that hospital officials would have undue worry that he would purposely escape from a field trip or attempt to harm others while out. it probably isn't any more
dangerous to send him out on a well-supervised field trip than it was to let him live in various minimally-supervised (compared to a mental hospital, anyway) housing situations.
...granted, I don't know what would have prompted hospital officials to let him leave the hospital in the first place, especially with his criminal history and the difficulty he and they experienced with medical management of his mental issues (and, of course, his previous escape attempts).
