A report by Wired says the filing "is the first indication that police cultivated an inside source prior to raiding the home of Gizmodo editor Jason Chen."
Wired was among the news organizations, led by the Associated Press and the LA Times, who requested that the court release the sealed search warrant affidavit that was used to raid Chen's house.
San Mateo County deputy district attorney Chris Feasel wrote that the media's right to access court documents does not outweigh the Peoples right to protect the sanctity of an ongoing investigation, nor does it outweigh the rights of the people to protect the identity of persons who may have provided information to law enforcement in confidence during the initial stages of investigation.
Chief deputy district attorney Stephen Wagstaffe earlier said the affidavit is "not a public record and thus is not subject to requests under any public-records act."
Prior to the Wired report noting an informant, it was understood that the affidavit was sealed primarily to prevent disclosure of the names of "two individuals of interest, whom police do not want to alert."
The EFF and other media groups have criticized the search as being improper because Chen's home office could be considered a newsroom, and therefore protected under shield laws designed to prevent police from investigating journalists' sources.
However, prosecutors say the search was related to a felony theft investigation rather than simply being an effort to determine Chen's sources as a journalist.