Credit Bryan R. Smith for The New York Times
WASHINGTON â The Justice Department is demanding Appleâs help in unlocking at least nine iPhones nationwide in addition to the phone used by one of the San Bernardino, Calif., attackers.
The disclosure appears to buttress the companyâs concerns that the dispute could pose a threat to encryption safeguards that goes well beyond the single California case.
Apple is fighting the governmentâs demands in at least seven of the other nine cases, Marc J. Zwillinger, a lawyer for the company, said in a letter unsealed in federal court on Tuesday.
âApple has not agreed to perform any services on the devices,â Mr. Zwillinger wrote. Starting in December, the letter says, Apple has in a number of cases objected to the Justice Departmentâs efforts to force its cooperation through a 1789 statute known as the All Writs Act, which says courts can require actions to comply with their orders.
In the San Bernardino case, prosecutors have cast their demands for Apple to help them unlock the iPhone used by Syed Rizwan Farook â one of the attackers in the December rampage, in which 14 people were killed â as a limited effort in response to an unusual situation.
Still, âno one should be surprised that weâre investigating other cases and looking for assistance in those other cases,â a law enforcement official said on Tuesday.
Since challenging a judgeâs demand in the San Bernardino case, which called for Apple to create a special tool to help investigators more easily crack the phoneâs passcode, the company has repeatedly asserted that such a move could not be done in isolation.
âOnce created, the technique could be used over and over again, on any number of devices,â Appleâs chief executive, Timothy D. Cook, said in a letter to customers. And in a note on its website on Monday, Apple said law enforcement agencies nationwide âhave hundreds of iPhones they want Apple to unlock if the F.B.I. wins this case.â
Apple has long maintained that it would hand over data to comply with a court order when it was technically able to do so. In a report covering the first six months of 2015, Apple said it had received nearly 11,000 requests from government agencies worldwide for information on roughly 60,000 devices, and it provided some data in roughly 7,100 instances.
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But while the data backed up on Appleâs iCloud service is readily accessible by the company, it has made the security on the iPhone itself increasingly hard to crack.
Because a number of the newly disclosed cases remain sealed, Appleâs letter did not describe the types of crimes at issue. But they appear to involve run-of-the-mill prosecutions for offenses like drug trafficking and pornography, rather than a high-profile terrorism investigation, officials said.
The newly disclosed cases are in New York, Chicago, Los Angeles, San Francisco and Boston.
The existence of the other demands came to light in a drug-trafficking case in Federal District Court in Brooklyn, where prosecutors are seeking access to the data held in an iPhone linked to a methamphetamine distribution ring.
The owner of the phone, Jun Feng, 45, has pleaded guilty to conspiracy in the case. But prosecutors have pushed ahead anyway with their efforts to force Apple to unlock his phone, in part because they maintain that it could lead them to other drug suspects.
The two sides are awaiting a ruling from Magistrate Judge James Orenstein on whether Apple should be forced to cooperate. Before issuing a ruling, Judge Orenstein wanted Apple to detail other pending requests from prosecutors.
The Brooklyn drug-trafficking case has been dwarfed by the fight in California. But national security lawyers say the Brooklyn case remains important, because Judge Orensteinâs decision is expected to be the first to publicly examine the governmentâs authority under the All Writs Act to force Apple to unlock passcode-protected iPhones.
The judge has indicated skepticism over the governmentâs demands. Initially, Apple agreed to a formal order to help the Justice Department gain access to Mr. Fengâs phone, but Judge Orenstein balked, questioning whether the All Writs Act could be used that way. He invited Appleâs lawyers to raise objections.
While his ultimate decision will not be legally binding in California, it could influence the legal arguments there. And an appeal by either side has the potential to work its way through the federal court system to become significant case law.
Law enforcement officials around the country are anxiously watching the cases in both Brooklyn and California to see how their own investigations might be affected.
At a news conference last week after the debate erupted in California, the New York City police commissioner, William J. Bratton, and the Manhattan district attorney, Cyrus R. Vance Jr., said they had collected about 175 iPhones, in investigations, that they have been unable to unlock.
Mr. Vance rejected the notion that Apple should be forced to cooperate only in certain prominent crimes.
âWhat we discover is that investigation into one crime often leads into criminal activity in another, sometimes much more serious than what we were originally looking at,â he said.