A federal judge on Tuesday ordered Apple to give investigators access to encrypted data on the iPhone used by one of the San Bernardino shooters, assistance the computer giant “declined to provide voluntarily,” according to court papers.

In a 40-page filing, the U.S. Attorney’s Office in Los Angeles argued that it needed Apple to help it find the password and access “relevant, critical … data” on the locked cellphone of Syed Farook, who with his wife Tashfeen Malik murdered 14 people in San Bernardino, California on December 2.

“Despite … a warrant authorizing the search,” said prosecutors, “the government has been unable to complete the search because it cannot access the iPhone’s encrypted content. Apple has the exclusive technical means which would assist the government in completing its search, but has declined to provide that assistance voluntarily.”