For months, the FBI pressured Apple to break security measures on an iPhone used in the San Bernardino attacks, only to call off the case at the last minute when it was presented with a third-party method for breaking into the phone. But while the bureau's legal arguments have been detailed exhaustively, it's remained silent on exactly what it expected to find on the phone, which was issued to the San Bernardino attacker Syed Farook by his employer.

But a new report suggests the phone has yielded almost no useful information. CNN is reporting that the phone didn't contain any previously unknown contacts or message data, citing anonymous law enforcement officials. Investigators were particularly curious about the period after the shooting, since metadata from a third-party app might reveal a previously unknown accomplice — but according to CNN's sources, there was simply nothing to find. That confirms a previous CBS News report that nothing of significance had been found on the phone. The police chief of San Bernardino had also speculated that no valuable evidence was likely to be found on the phone prior to the new method being used.

"We can't look the survivors in the eye, or ourselves in the mirror, if we don't follow this lead."

CNN emphasizes that the phone was still useful in confirming that the San Bernardino attackers didn't contact outside parties for help, particularly during the immediate aftermath of the attack. The phone does contain data not present in the previously obtained iCloud backups, but that shouldn't be surprising since Farook continued to use the phone for several weeks after the most recent backup. And judging by the state of the investigation, there's no use for any of that data. Since both perpetrators of the attack are dead, the evidence isn't needed for trial, and there are no new leads for further investigation.

The result is an anti-climactic end to a major standoff between Apple and the FBI in San Bernardino. While the legal issue was still before the judge, FBI director Comey repeatedly argued that the evidentiary value of the phone justified any potential threat to Apple. "Fourteen people were slaughtered and many more had their lives and bodies ruined. We owe them a thorough and professional investigation under law," Comey wrote in February. "We can't look the survivors in the eye, or ourselves in the mirror, if we don't follow this lead."

Now that the lead has turned up empty, the future of the FBI's encryption fight is uncertain. The government is still seeking to appeal a New York ruling that denied a request to break security on a separate iPhone, but it's unclear whether the higher courts will take up the appeal.