JEFFERSON COUNTY, Colo. (KDVR) — FOX31 learned new details about what led to the arrest of three high school seniors suspected of a rock-throwing crime spree that killed a 20-year-old woman.

Arrest documents released Thursday show investigators used cell phone towers to track down the suspects and match their location to where the crimes occurred. 

According to the affidavit, detectives requested a “tower dump,” which shows all the data recorded by a single cell phone tower during a specific time frame.

Eleven phone numbers bounced off the four cell phone towers in question, according to the affidavit.

“One in particular showed a path that travelled the same time frames of the incidences reported using the four towers, and that phone passed the area of the death of the victim at the same time that the victim, Alexa, stopped talking,” the document reads. That phone reportedly belonged to one of the suspects, Joseph Koenig.

‘Reverse warrants’ undecided in the courts

“These kinds of warrants are often referred to as reverse warrants,” University of Denver professor Ian Farrell said. “Because usually you have the suspect and you’re trying to find information. Here, you have information, and you’re trying to use that to identify the suspect.”

Farrell said a specific phone pinging to a crime scene is not enough to issue an arrest warrant, but it can allow investigators to focus on potential suspects and search for additional evidence.

“Law enforcement is always cumulative in this situation. You find a piece of information that’s a lead, that leads you to other information. That then is a further lead, and that’s how a case is built,” he said.

Farrell said this type of search is quite controversial. It’s similar in nature to so-called “keyword warrants” used in the identification of three teen suspects in a deadly 2020 Denver arson in Green Valley Ranch.

He expects the issue to be heard by the U.S. Supreme Court in the years to come as it looks to balance privacy and public safety.

“That balance is the challenge,” he said. “Finding the appropriate balance there, and of course, people disagree about where that particular balance point is, that point of equilibrium, including different members of the court.”