Apple has filed a motion in court asking a federal magistrate to reverse her order that the company help the FBI hack into a killer's locked iPhone.
The computer giant rejected the government's request to create new software that would allow law enforcement officials to break into the iPhone 5c belonging to Syed Rizwan Farook, who along with his wife, Tafsheen Malik, killed 14 people in San Bernardino, California, last year.
In court briefs filed Thursday, lawyers for Apple argued that the government's request "creates an unprecedented burden on Apple and violates Apple's First Amendment rights against compelled speech."
Apple has said the FBI is asking for what amounts to a back door around the company's security measures, and that, in the wrong hands, in the future that software would make countless Apple users vulnerable to searches of their phones.
"No court has ever authorized what the government now seeks, no law supports such unlimited and sweeping use of the judicial process, and the Constitution forbids it,'' the company's lawyers said.
In Washington on Thursday, the head of the FBI acknowledged that forcing Apple to help investigators access the locked iPhone would set a legal precedent, and he could not promise that it would be the only time the bureau would request such help.
James Comey called the standoff with the company "the hardest problem I've seen in government."
The dispute is the latest to showcase the frustrations of law enforcement officials who complain that newer encryption methods used by companies like Apple make it harder to carry out investigations involving the use of technology by criminal suspects.
Apple strengthened encryption of its phones in 2014 amid increased public concern about digital privacy.