It's quite possible that this guy is psychotic, in combination with being obsessed with this crime. Sounds like he had a past obsession with the Polly Klaas case, as well. I hope they have more than his "confession". I really don't understand why they didn't try to first establish whether he could have been in Boulder at that time. Also, they could have taken a sample over there for the DNA test. If they had to bring him back, they could have done it based on the child porn and then investigated further without making the possible JBR connection public. None of this makes sense to me.
Could be that Cunningham (in article) is right, ie. that arranging detention/extradition on a child porn charge was not do-able, but basing it on a murder charge would guarantee the desired result.