I can see your point. 'Looking At Porn' and 'Engaging In Sex Orgies', although they are both catagorizable as irregular sexual activities, are nonetheless slightly different kettles of fish.
Among American males, 15 to 115, you'd be hard pressed to find anyone who hasn't sneaked a peek at a dirty picture or two at some point...
And -in most cases- it has resulted in no serious, lasting damage to their personalities.
People who engage in sex orgies, on the other hand, are in the minority. And participation in activities such as this requires a much deeper commitment than sneaking a peek at a dirty picture.
"...They are established sexual "experimentors" who use the ACT of sexual intercourse with people other than their spouses to further gratify themselves. How far would they go to further gratify themselves after "swinging" was getting dull and routine?..."
Yes, some people tend to graduate from one level of a given activity to the next. It's often true among drug users and criminals, and must be equally true of sexual miscreants as well.
But -depraved as they are- the majority of swingers are probably not likely to 'graduate' all they way to sex-murder...
YES, I believe that a HIGHER PERCENTAGE of them are capable of such complete degradation when compared to their less perverse fellow citizens. I'm on record with respect to believing that. But I believe that most swingers tend reach a point where they become comfortable with a particular set of fetishes and then stick with that repertoire.
I don't think it was one of the 'regulars' that did it. The little girl was killed by a wild card, someone who they brushed up against who was a sexual predator of the first order.
If I were the detective in charge, I'd have gotten a list of their one night stands. I'd have asked the VD's for the names or descriptions of the ones who gave them the creeps, who were never invited back for 'seconds'.
Does the accused fit this description? I'm not sure. There seems to be an element of this in his relationship with the VD's. (from what I've read)