WESTMINSTER - A little-discussed technique of mining data from cell phone towers was used extensively in the search for the killer of Jessica Ridgeway, according to newly-unsealed court documents reviewed by 9Wants to Know.
The FBI along with local law enforcement agencies asked a federal court for at least four "cell tower dumps" in an effort to connect cell phone users to four distinct crime scenes. While it remains unknown just how many individual cell phone ID's were gathered in October of 2012, it's widely assumed the collection netted "thousands." The practice, according to a spokesperson for the FBI, is only used "under extreme circumstances when there is concern for public safety."
Tower dumps allow law enforcement to collect data from individual cell phone towers. The data, for instance, will tell investigators if a particular cell phone was operational near the vicinity of a particular cell phone tower. During the massive search for Jessica Ridgeway, investigators were anxious to talk to people whose cell phones were used at or near the time of key developments in the case.
It is why, for example, they asked five cell phone carriers for the tower data from October 5, 2012, between the times of 7:00 a.m. and 9:30 a.m. near the location of Jessica's disappearance. Westminster Police and a representative for the FBI both told 9News the practice is an "investigative technique," and thus declined a request to discuss it in more detail.
Brian Owsley is a former federal Magistrate and current visiting professor at Texas Tech University's School of Law. He has studied "tower dumps" extensively. Owsley told 9News he believes investigators in Colorado properly used the practice in what was clearly a vast and time-sensitive investigation, but he worries what can happen when tower dumps are used improperly.
"People might not want their information compromised in some way," he said. "What's happening to all of this information that's gathered by law enforcement agencies?"
The FBI, through a local spokesperson, did tell 9News individual cell phone numbers are not collected as part of initial tower dumps. Only an "electronic ID" is collected. Owsley said the practice will likely only become more commonplace.
"This is a relatively new surveillance technique," he said. "It is becoming more and more common."
He also said it's not widely understood.
"I would say that's a good characterization. It's now a secret. It's not well known," he said.
In the end, the collection of data from the massive cell phone dumps did not directly lead investigators to Austin Sigg. Ironically, it was a phone call initially made by his mother to 911 that ultimately gave investigators their suspect.
A day after Austin Sigg's mother placed that call to police telling them her son wanted to turn himself in, police say they were finally able to match Austin Sigg's DNA (collected a few days earlier after a general inquiry to his house) to DNA found at a trio of crime scenes. Had it not been for the phone call, investigators believe the DNA collection would have ultimately led them to Sigg. Technology, they say, still has its place in fighting crime.
(KUSA-TV © 2013 Multimedia Holdings Corporation)