Months after the San Bernardino attacks, the FBI still can't get into one of the shooter's phones

It's been months since two shooters attacked a community center in San Bernardino, California. And law-enforcement officials still can't get into the phone of one of the killers, FBI Director James Comey told a Senate committee on Tuesday.

Although law enforcement has the authority to access the phone, they haven't been able to get past the locking feature on the device. Comey said that law enforcement is still working to access the data in the phone.

"The growing use of encryption both to lock devices when they sit there and to cover communications … is actually overwhelmingly affecting law enforcement," Comey told the Senate Intelligence Committee.

Phones that default-lock when they're not being used have especially been a problem - not only for national-security investigations, but also for local law-enforcement agencies.

"Those devices are going to hold the evidence of child pornography, communications that somebody made before they were killed, before they went missing, the evidence necessary to solve a crime," Comey said. "It's a big problem for law enforcement, armed with a search warrant, when you find a device that can't be opened even though the judge said there is probable cause."

This includes the cell phone of one of the San Bernardino shooters.

David Bowdich, assistant director of the FBI's Los Angeles bureau, told reporters in early December that police found two crushed cellphones in a trash can near the site of the attack. They retained the cell phones, and Bowdich said that law enforcement would " continue to exploit the data" from them.

But this is evidently proving difficult.

"We still have one of those killers' phones that we have not been able to open," Comey said. "It's been over two months now. We're still working on it."

Bowdich said in December that law enforcement "uncovered evidence that these subjects have attempted to destroy their digital fingerprints."

Syed Rizwan Farook, a 28-year-old US citizen, and Tashfeen Malik, his 27-year-old wife, died in a shootout with police after they carried out the December attack at the Inland Regional Center. The attack killed 14 people and left at least 21 others injured.

The shooters pledged allegiance to the terrorist group ISIS (also known as the Islamic State, ISIL, or Daesh) right before the attacks.