United States v. Forrester
United States Court of Appeals for the Ninth Circuit
512 F.3d 500 (9th Cir. 2008)
Suspecting Forrester and Alba (defendants) of manufacturing Ecstasy, the government had Alba's internet service provider install a 'mirror port' that let investigators see the to/from addresses on Alba's emails, the IP addresses (though not the specific pages) of websites Alba visited, and the total volume of data sent to or from his account, without capturing any actual message content or specific web pages read. Based partly on this surveillance, the defendants were convicted, and they appealed, arguing the monitoring violated their Fourth Amendment rights.
Whether the government may monitor without a warrant the to/from addresses in a suspect's emails, the IP addresses of websites the suspect visits, and the total volume of information sent to or from the suspect's ISP account.