I saw this Law & Order Criminal Intent episode this afternoon for the first time and was struck by its similarity to the Season 4 X-Files episode called "Paper Hearts" -- so much so that I immediately watched the X-Files DVD afterward to be sure. Not only is the storyline almost identical, but entire sections of dialogue were lifted almost line-for-line from "Paper Hearts."
My fiancé hadn't seen the X-Files episode before and was amazed by the parallels (or, as he called them, the ripoffs) when he watched it. I was able to predict just about every plot turn beforehand by remembering what happened on the X-Files episode!
I can't imagine we are the first people to have noticed this. Just out of curiosity, I've spent some time this evening searching for a six-degrees-of-separation kind of thing between the writers of this ep and of X-F, but haven't found any yet.