Interesting Sixth Circuit Decision on Probable Cause:
The Case: United States v. Hodson (6th Cir., Sept 19, 2008).

  The Panel: Judges Batchelder, Norris, and Gibbons.

  The Facts: Undercover agent posing as 12 year-old boy is exchanging instant messages online over AOL with someone using the screenname "WhopperDaddy." "WhopperDaddy" states to the boy that he "favored young boys, liked looking at his nine- and eleven-year-old sons naked, and had even had sex with his seven-year-old nephew." The suspect then "expressed his desire to perform oral sex" on the boy.

  The undercover agent subpoenas AOL, finds the address of the suspect based on the billing information on the credit card used for billing, and a few weeks later executes a warrant at the home for child pornography. The search uncovers imagines of child pornography, and the defendant is convicted of possessing the images.

  The Legal Issue: The defendant appeals, arguing that that the warrant affidavit lacks probable cause that child porn would be in the home, and that no reasonable officer could have a good faith belief that the warrant contained probable cause.

  The Holding: Conviction reversed, as there was no probable cause and no reasonable officer would think there was:
  It is beyond dispute that the warrant was defective for lack of probable cause — Detective Pickrell established probable cause for one crime (child molestation) but designed and requested a search for evidence of an entirely different crime (child pornography). Consequently, the warrant did not authorize the search and, barring some other consideration, the evidence obtained during that search must be excluded from trial. The question presently before us is whether any other consideration — specifically, the Leon good-faith exception — can overcome the defect and justify admission of the evidence anyway. For the reasons that follow, we conclude that it cannot.
  The question we address here is whether the faceless, nameless “reasonably well trained officer” in the field, upon looking at this warrant, would have realized that the search described (for evidence of the crime of child pornography) did not match the probable cause described (that evidence would be found of a different crime, namely, child molestation) and therefore the search was illegal, despite the magistrate’s decision to the contrary. We conclude that any “reasonably well trained officer” would certainly have come to that realization if presented with this warrant.
  Otherwise stated, we conclude that it was unreasonable for the officer executing the warrant in this case to believe that probable cause existed to search Hodson’s computers for child pornography based solely on a suspicion — albeit a suspicion triggered by Hodson’s computer use — that Hodson had engaged in child molestation.
  My Take: When a law-and-order panel reverses a criminal conviction on procedural grounds, it's pretty tempting to say it must be right and to just leave it alone. But I'm actually not so sure the panel was correct.

  The court reversed the conviction on the ground that the affidavit established probable cause for one crime (child molestation) but asked for evidence of another crime (child pornography) without explaining the gap. But at least off the top of my head, I'm not aware of caselaw for the view that probable cause can be divided so sharply. The target did more than just admit to past child sex activities in the past. While chatting via AOL instant message, he "expressed interest" in performing sex an undercover agent who he thought was a 12 year old boy.

  Is it really such a stretch to think that someone who does such a thing would have child pornography images somewhere in the home? Based on reading a lot of these cases (and working on some when I was at DOJ), I would be rather surprised if such a person didn't collect images, actually. Even the Supreme Court has linked the two. See Osborne v. Ohio, 395 U.S. 103 n.7 (1990) ("Child pornography is often used as part of a method of seducing child victims. A child who is reluctant to engage in sexual activity with an adult or to pose for sexually explicit photos can sometimes be convinced by viewing other children having "fun" participating in the activity.").

  I think it's fair to say the evidence presented wasn't strong enough to establish probable cause. But at least off the top of my head, I would think that there was enough there to satisfy the Leon good faith test. Or am I thinking of this the wrong way?