Apple's Touch ID feature has become central in a case against an alleged pimp in Texas, as Jennifer McCarty of the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives compelled the accused, Martavious Keys, to use his fingerprints as a means to unlock his iPhone 5s, which is suspected to contain incriminating information.

Keys, who lives in Dallas, was arrested on May 19 for allegedly trafficking two girls, aged 14 and 15. According to court documents that were recently released, Keys had forced the two underage girls to engage in sexual acts with men, who paid him $150 a session. According to the two girls, the abuse lasted for months, and during that time, they were forced to do drugs against their will.

The alleged pimp had his iPhone 5s with him during his arrest, and a week later, on May 26, prosecutors asked U.S. Magistrate Judge Irma Ramirez to force Keys to unlock his smartphone using Touch ID. Prosecutors believe that Keys' mobile device held enough contacts, photos, emails and text messages to properly incriminate him.

The approval for the prosecutors' request was granted on June 1. However, investigators were ultimately unable to unlock the device.

"Unable to obtain forensic acquisition of the described device," the investigators' report stated.

The failure to unlock Keys' iPhone 5s is suspected to be due to the smartphone's security feature, which entails that a user input both the fingerprint and a passcode to properly unlock a device after a 48-hour period. Since the phone had been unused since Keys' arrest, the suspect needed both his fingerprint and his passcode to unlock the mobile device.

Unfortunately, while compelling a suspect to input his or her fingerprint as a means to aid investigators, inputting a passcode is a completely different matter. Indeed, a number of legal scholars have stated that forcing someone to turn over their passcode, regardless of circumstances, is a constitutional violation. Attorney Marcia Hofman describes this gray area in the constitution.

"We can't invoke the privilege against self-incrimination to prevent the government from collecting biometrics like fingerprints, DNA samples, or voice exemplars. Why? Because the courts have decided that this evidence doesn't reveal anything you know," she said.

Martavious Keys was nonetheless indicted on June 7, with his trial set to begin on Aug. 15, 2016.