According to the DOJ, the Sarbanes-Oxley Act, a federal law passed in the wake of the Enron scandal, makes it a crime to delete your browser history if the federal government might want it for a criminal investigation, even if you don't know that the investigation exists. A former friend of Tamerlan Tsarnaev, 24 year old Khairullozhon Matanov, is facing decades in prison for doing just that.
Juliana DeVries reports for the Nation:
The night of the Boston Marathon bombings, [Matanov] ate dinner with Tamerlan and Dhzokhar Tsarnaev at a kebob restaurant in Somerville. Four days later Matanov saw photographs of his friends listed as suspects in the bombings on the CNN and FBI websites. Later that day he went to the local police. He told them that he knew the Tsarnaev brothers and that they’d had dinner together that week, but he lied about whose idea it was to have dinner, lied about when exactly he had looked at the Tsarnaevs’ photos on the Internet, lied about whether Tamerlan lived with his wife and daughter, and lied about when he and Tamerlan had last prayed together. Matanov likely lied to distance himself from the brothers or to cover up his own jihadist sympathies—or maybe he was just confused.
Then Matanov went home and cleared his Internet browser history.
Matanov continued to live in Quincy for over a year after the bombings. During this time the FBI tracked him with a drone-like surveillance plane that made loops around Quincy, disturbing residents. The feds finally arrested and indicted him in May 2014. They never alleged that Matanov was involved in the bombings or that he knew about them beforehand, but they charged him with four counts of obstruction of justice. There were three counts for making false statements based on the aforementioned lies and—remarkably—one count for destroying “any record, document or tangible object” with intent to obstruct a federal investigation. This last charge was for deleting videos on his computer that may have demonstrated his own terrorist sympathies and for clearing his browser history.
Matanov faced the possibility of decades in prison—twenty years for the records-destruction charge alone.
Read more about the Matanov case.