Law enforcement agencies are more and more often using the social media site Facebook in criminal investigations and obtaining warrants to search defendants' private Facebook sites. A recent article in the International Business Times reports that often a person and their lawyer do not even know that their Facebook profile has been searched by police.
According to the IBT article, a review was done by Reuters of the Westlaw legal database to find out how many search warrants had been granted for a search of a private Facebook account. The investigation showed that there were 11 authorized warrants for this kind of search in 2011. The number of requests and authorizations are increasing because there were half that number granted in 2010. Crimes being investigated through these warrants included rape, arson and terrorism charges and the investigating agencies included the FBI, ICE and the DEA.
According to the IBT, the searches have not been challenged on the grounds of illegal search and seizure -- a violation of the Fourth Amendment, but this may be because many people do not even know that a search happened.