Last night in Houston two masked men, armed with a revolver and a shotgun, stormed a Denny's and raided the cash register. The same scene has played out on security footage at dozens of Houston-area IHOPs and Denny's, albeit occasionally with bloodshed.

Houston police officer James Taylor, testifying before a Texas Senate committee this morning, said the department's investigative efforts have been fatally hamstrung by its inability to acquire cell-phone location data without a warrant.

"The inability for us to access data has led us to being unable to catch them," Taylor told the committee.

See also: A Reminder That Texas Cops Still Don't Need a Warrant to Collect Cell-Phone Metadata

It's not just making it harder to identify suspects, Taylor said. It makes it practically impossible in some cases, "which results in people dying."

That's the argument being pushed by Texas police and prosecutors as they gear up for a fight against efforts to limit cops' access to cell-phone metadata -- the call logs, location data and other records (not including the content of phone calls or text messages) phone companies collect from consumers. They say that a bill requiring search warrants for emails also required search warrants for cell phone metadata.

The problem with the argument, privacy advocates say, is that it's bullshit.

Scott Henson, who blogs about criminal justice issues at Grits for Breakfast and is a founding member of the Texas Electronic Privacy Coalition, stopped shy of calling Taylor a liar during his own testimony this morning, but only just. The bill introduced last session that would have required cops to obtain a warrant before accessing a customer's data died last session despite overwhelming support from legislators, and a recent state appeals court decision makes clear that no warrant is required.

Police might be saying otherwise, but "the courts are interpreting it completely differently."

The debate over whether warrants are currently required is a bit of a head spinner. (Cops are in the paradoxical position of arguing both that warrants are necessary to obtain cell-phone metadata and that they will fight efforts during the 2015 legislative session to require warrants for cell-phone metadata). But both sides agree that the battle is an important one.

Acquiring a search warrant requires cops to establish probable cause. In the case of cell phone records, this would mean first establishing enough facts to suggest to a judge that the phone's owner is a suspect or that they're in possession of important evidence.

Bill Exley, an assistant district attorney in Harris County, told the committee that cops typically haven't yet established probable cause when they start sifting through metadata.

"The way we use these records is to gather the evidence that leads to probable cause."

As an example, Taylor gives a hypothetical example of a Denny's and an IHOP on opposite sides of the city being robbed on consecutive nights. Investigators could get a list of the phones that were communicating with cell towers near each restaurant, find the ones that were in both places at both times, and potentially narrow down the list of potential suspects.

"That would be a clue," Taylor said. "Otherwise we'd have to wait until a mad girlfriend calls Crimestoppers or they get in a car wreck."

Police also stress that this isn't up-to-the-second GPS data they're requesting, which requires a warrant. It's a phone's relative distance from cell towers that is hours or days old.

Matthew Henry, an attorney who represents Austin-based Data Foundry, worried that, while that example seems harmless enough, there's nothing in state or federal law preventing cops from acquiring a trove of historical location data and call logs and using it to establish an intimate portrait of one's daily existence.

"Any cell phone-location statute that requires a warrant should have exceptions for exigent circumstances," Henry said, referring to crisis scenarios like kidnappings in which cops need to immediately locate a suspect or victim. "What there shouldn't be exceptions for is when law enforcement wants to get location history. ... They fall under the protection of the Fourth Amendment and should be protected by a warrant requirement."

Send your story tips to the author, Eric Nicholson.