Operation Candyman (which Lawmeme previously mentioned here) is an FBI investigation into an alleged child pornoraphy ring. In January 2001, FBI agents identified several Yahoo Groups that seemed to involve posting and exchanging child pornography. One of the largest groups was the Candyman group, which became the focus of the FBI's investigation. The FBI issued a court order to Yahoo and managed to retrieve 7,000 unique email addresses that had registered with the group. The FBI then issued subpoenas to various ISPs and retrieved the email users' addresses. Based solely on the fact that these emails appeared in the Candyman group's registration list, the FBI obtained search warrants and busted into various people's houses, including the house of one Harvey Perez, although Perez had neither sent nor received emails containing child porn images.
Today, a federal district judge in New York threw out the evidence that the government had collected against Perez, saying that the FBI had failed to show probable cause to justify the search warrant. The presence of Perez's email on the Candyman list was simply insufficient without further evidence that he in fact engaged in trading child pornography.
This decision could have potentially far-reaching effects: 700 copies of Perez's affidavit were circulated among FBI offices around the country.
The New York Times article is here.