Generally speaking, government agencies (including police and federal law enforcement agencies) are required to obtain a search warrant before conducting a search of an individual's private property. When evidence is obtained without a warrant, it could be suppressed at trial.
But there are gray areas when it comes to how the existence of illegal material is brought to the attention of law enforcement agencies. Back when photo film needed to be developed, for instance, photo mats would often coordinate with law enforcement if they happened to come across pictures that were potentially child pornography. In the digital age, the relationship between private companies and law enforcement agencies has become significantly more complicated.
In one recent case alleging possession of child pornography, defense attorneys are questioning the link between the FBI and Best Buy's "Geek Squad," one of the most popular computer repair services in the country. It is already Best Buy policy to turn over suspected child pornography to authorities if it is discovered in the normal course of fixing a customer's computer. This seems consistent with the "plain view" doctrine that says police can search and seize illegal material without a warrant if it is already in plain view.
But the relationship between the FBI and the Geek Squad is allegedly not limited to turning over child pornography that is in "plain view." Instead, it seems as though the FBI had turned certain Best Buy employees into confidential, paid informants.
This is important for a number of reasons. First of all, if a Best Buy employee is being paid for turning over information, this essentially makes them an agent of the government. In such cases, a warrant should be required before a search can be conducted. Second, if a Best Buy employee is being compensated to turn over cases of suspected child pornography, this compensation could encourage paid informants to conduct much more thorough searches of a customer's hard drive than would be required to fix whatever technical problem was presented.
The particular criminal case in question could set important precedents in future cases involving private companies and searches of hard drives. But in the meantime, all Americans should realize that their supposedly private digital data may not remain private.