Shocking revelations about creepy government surveillance came in waves over the summer, from the Snowden leaks to the Hemisphere Project , through which the government has paid AT&T for access to a mind-bogglingly vast database of our telephone calls. In many cases of new surveillance technologies like Hemisphere, there are serious constitutional concerns that courts have not yet reviewed. That's where we come in.

Today the ACLU and the Electronic Frontier Foundation filed an amicus brief in United States v. Diaz-Rivera, a criminal case that could present the first opportunity for a court to review the constitutionality of the Hemisphere Project (you can read the brief here).

Hemisphere is deeply troubling, not only because the government is amassing detailed, comprehensive information about people who've done nothing wrong, but also because the government has deliberately kept Hemisphere secret, even from criminal defendants who've been subjected to the program.

The ACLU/EFF amicus brief urges the Court to disclose all sources of the extensive cell phone surveillance conducted in Diaz-Rivera, including the extent to which the government relied on Hemisphere or any other surveillance program in this investigation. Criminal defendants have the right to challenge unconstitutional surveillance programs to which they were subjected, but to do so, they need all the facts. The government should not be able to conduct unlawful surveillance, and then avoid legal challenges by hiding the truth.

What's at stake here? The privacy rights of, well, just about everyone who uses a phone.

In early September, The New York Times revealed the existence of "Hemisphere," a database of telephone call records that's the Big Brother to the NSA's controversial mass call-tracking program . Through Hemisphere, the government pays AT&T employees to work with DEA and other law enforcement personnel and to provide them with access in drug investigations to a vast database of call records going back to 1987. By analyzing calling patterns across the database, the government is able to determine when the target of an investigation has started using a new phone.

As my colleague Catherine Crump explained in a piece on Slate , "to locate the tiny number of people who evade law enforcement agents by [frequently changing phones], an AT&T-government partnership is sifting through sensitive phone records of vast numbers of people."

Equally troubling, the government is taking affirmative steps to hide the existence of the program. According to documents obtained by the New York Times, agents using Hemisphere were "instructed to never refer to Hemisphere in any official document."

Diaz-Rivera is a criminal prosecution for drug distribution and other drug-related offenses. The original indictment named 20 defendants. The investigation relied heavily on cell phone surveillance. The government disclosed to defendants that it acquired records for almost 750,000 phone calls from 643 unique numbers. But the government has not explained how it acquired all of this cell phone data.

For example, the government provided the defendants with court orders authorizing the collection of call data from only 52 phones; meaning it acquired call data from 591 numbers not specified in any court order.

In addition, the government repeatedly obtained new telephone numbers used by the targets of its investigation, just days after they stopped using old phones, and without any real explanation about how it accomplished this feat.

While the government has not explained how it acquired all of this information, the gaps in the story sound a whole lot like they were filled by Hemisphere, which provides the government with access to data about all calls that pass through an AT&T switch and is used most frequently in drug investigations to identify "burner" replacement phones.

If the government is going to use a surveillance program to prosecute someone criminally, it needs to disclose the full extent of the surveillance. As we point out to the Court in our brief:

"If the government is able to hide this information even from criminal defendants who have been subjected to intrusive surveillance, then these practices will escape all court review and the executive will effectively be allowed to make surveillance law unilaterally and secretly. Our constitutional system does not tolerate such a result."

We all have a Fourth Amendment right to be free from unconstitutional surveillance. But most of us would never be able to bring a legal challenge because we'll never know if we were illegally spied on.

Unless the Court requires the government to disclose information about the surveillance it used to further the investigation in this case, all our privacy rights will suffer.