The Colorado prosecution of a woman accused of a mortgage scam will test whether the government can punish you for refusing to disclose your encryption passphrase.

The Obama administration has asked a federal judge to order the defendant, Ramona Fricosu, to decrypt an encrypted laptop that police found in her bedroom during a raid of her home.

Because Fricosu has opposed the proposal, this could turn into a precedent-setting case. No U.S. appeals court appears to have ruled on whether such an order would be legal or not under the U.S. Constitution's Fifth Amendment, which broadly protects Americans' right to remain silent.

In a brief filed last Friday, Fricosu's Colorado Springs-based attorney, Philip Dubois, said defendants can't be constitutionally obligated to help the government interpret their files. "If agents execute a search warrant and find, say, a diary handwritten in code, could the target be compelled to decode, i.e., decrypt, the diary?"

To the U.S. Justice Department, though, the requested court order represents a simple extension of prosecutors' long-standing ability to assemble information that could become evidence during a trial. The department claims:

Public interests will be harmed absent requiring defendants to make available unencrypted contents in circumstances like these. Failing to compel Ms. Fricosu amounts to a concession to her and potential criminals (be it in child exploitation, national security, terrorism, financial crimes or drug trafficking cases) that encrypting all inculpatory digital evidence will serve to defeat the efforts of law enforcement officers to obtain such evidence through judicially authorized search warrants, and thus make their prosecution impossible.

Prosecutors stressed that they don't actually require the passphrase itself, meaning Fricosu would be permitted to type it in and unlock the files without anyone looking over her shoulder. They say they want only the decrypted data and are not demanding "the password to the drive, either orally or in written form."

The question of whether a criminal defendant can be legally compelled to cough up his encryption passphrase remains an unsettled one, with law review articles for at least the last 15 years arguing the merits of either approach. (A U.S. Justice Department attorney wrote an article in 1996, for instance, titled "Compelled Production of Plaintext and Keys.")

Much of the discussion has been about what analogy comes closest. Prosecutors tend to view PGP passphrases as akin to someone possessing a key to a safe filled with incriminating documents. That person can, in general, be legally compelled to hand over the key. Other examples include the U.S. Supreme Court saying that defendants can be forced to provide fingerprints, blood samples, or voice recordings.

On the other hand are civil libertarians citing other Supreme Court cases that conclude Americans can't be forced to give "compelled testimonial communications" and extending the legal shield of the Fifth Amendment to encryption passphrases. Courts already have ruled that that such protection extends to the contents of a defendant's mind, so why shouldn't a passphrase be shielded as well?

In an amicus brief (PDF) filed on Friday, the San Francisco-based Electronic Frontier Foundation argues that the Justice Department's request be rejected because of Fricosu's Fifth Amendment rights. The Fifth Amendment says that "no person...shall be compelled in any criminal case to be a witness against himself."

"Decrypting the data on the laptop can be, in and of itself, a testimonial act--revealing control over a computer and the files on it," said EFF Senior staff attorney Marcia Hofmann. "Ordering the defendant to enter an encryption password puts her in the situation the Fifth Amendment was designed to prevent: having to choose between incriminating herself, lying under oath, or risking contempt of court."

The EFF says it's interested in this case because it wants to ensure that, as computers become more portable and encrypting data becomes more commonplace, passphrases and encrypted files receive full protection under the Fifth Amendment.

Because this involves a Fifth Amendment claim, Colorado prosecutors took the unusual step of seeking approval from headquarters in Washington, D.C.: On May 5, Assistant Attorney General Lanny Breuer sent a letter to John Walsh, the U.S. Attorney for Colorado, saying "I hereby approve your request."

While the U.S. Supreme Court has not confronted the topic, a handful of lower courts have.

In March 2010, a federal judge in Michigan ruled that Thomas Kirschner, facing charges of receiving child pornography, would not have to give up his password. That's "protecting his invocation of his Fifth Amendment privilege against compelled self-incrimination," the court ruled (PDF).

A year earlier, a Vermont federal judge concluded that Sebastien Boucher, who a border guard claims had child porn on his Alienware laptop, did not have a Fifth Amendment right to keep the files encrypted. Boucher eventually complied and was convicted.

One argument published in the University of Chicago Legal Forum in 1996--constitutional arguments among legal academics have long preceded actual prosecutions--says:

The courts likely will find that compelling someone to reveal the steps necessary to decrypt a PGP-encrypted document violates the Fifth Amendment privilege against compulsory self-incrimination. Because most users protect their private keys by memorizing passwords to them and not writing them down, access to encrypted documents would almost definitely require an individual to disclose the contents of his mind. This bars the state from compelling its production. This would force law enforcement officials to grant some form of immunity to the owners of these documents to gain access to them.

Translation: One way around the Fifth Amendment is for prosecutors to offer a defendant, in this case Fricosu, immunity for what they say. But it appears as though they've stopped far short of granting her full immunity for whatever appears on the hard drive (which may not, of course, even be hers).

Fricosu was born in 1974 and living in Peyton, Colo., as of last fall. She was charged with bank fraud, wire fraud, and money laundering as part of an alleged attempt to use falsified court documents to illegally gain title to homes near Colorado Springs that were facing "imminent foreclosure" or whose owners were relocating outside the state. Some of the charges include up to 30 years in prison; she pleaded not guilty. Her husband, Scott Whatcott, was also charged.

A ruling is expected from either Magistrate Judge Michael Hegarty or District Judge Robert Blackburn.

Jennifer Guevin contributed to this report.