I think he was the killer. I also think that JBR's father hatched up the plot.
Tinfoil hat time:
JNR's mother took little Joan to all these pageants. The father got jealous of the little tyke taking all of mommy's time and cooked up a murder so he could get his wife back. The wife knew nothing of this.
He knew Karr, knew that he was a kiddy toucher, got in touch with him, and paid him off with his bonus check, threatening to go to the cops about Karrs kiddy touching if he didn't go along with the plot. (Ransom note with exact dollar amount of bonus)
Mom was gone from the house, Karr came in, killed the kid and took off. Dad was probably upstairs watching TV.
Karr, as to not wanting to implicate the father, when caught, made up this story. The story is false, therefore Karr will not be convicted of anything other than being a lunatic seeking attention. Since there is no evidence, Karr will be let go, the father not implicated and the Jon Benet Ramsey case will be forever gone.
I hope you are not serious.
Karr's latest version (FoxNews) is that he was in the house all evening, and was even hiding in the house when the Ramsey's came in that night.