The US Government Has Asked a Court to Force Apple to Unlock the San Bernardino iPhone

The US Department of Justice has filed a motion seeking to force Apple to comply with a judge's order for the company to unlock the iPhone belonging to one of the San Bernardino shooters, according to a court document filed Friday.

The FBI is seeking the tech giant's help to access the shooter's phone, which is encrypted. The company so far has pushed back, and on Thursday won three extra days to respond to the order.

Immediately after the news broke on Friday, the price of Apple shares did not show signs of reacting to the injunction, first trading down by 0.1 percent and then hovering around zero.

A federal court hearing has been scheduled for March 22, according to Thom Mrozek, a spokesman for the US Attorney's Office for the Central District of California.

Earlier this week, that issued an order telling Apple it had to comply with the request, but Apple has so far refused.

The confrontation has pitted privacy advocates, who do not want to give any ground to government efforts to undermine encryption, and law enforcement officials who say people's lives may be at stake unless the shooter's iPhone is unlocked.

"Rather than assist the effort to fully investigate a deadly terrorist attack … Apple has responded by publicly repudiating that order," prosecutors wrote in the Friday order.

"Apple's current refusal to comply with the court's order, despite the technical feasibility of doing so, instead appears to be based on its concern for its business model and public brand marketing strategy," prosecutors added.

On Tuesday, Apple Chief Executive Tim Cook published a letter to customers saying that the company would fight the court order. The iPhone belonged to Syed Rizwan Farook, who along with his wife shot and killed 14 people last December in an attack that authorities said was inspired by the Islamic State. Both Farook and his wife were killed in a shootout with police.

The phone technically belonged to Farook's employer, the San Bernardino County Department of Public Health. The agency consented to a search and the FBI obtained a warrant, but, according to court documents, the feds claim they don't know the phone's passcode. If they input the wrong code more than 10 times, the phone could make its data permanently inaccessible. Hacking into it without using Apple-certified technology would theoretically also result in the phone wiping its data.

So the FBI asked a federal court in Los Angeles to compel Apple to help, which led to the current legal dispute between the government and the world's largest tech company.

It was not immediately clear whether the new motion was legally necessary. A footnote in the Justice Department's filing acknowledged a separate compel order "is not legally necessary."

Related: The Fight Between Apple and the FBI Could Shape the Future of Digital Privacy