How police searching for Nancy Guthrie are sorting through evidence, according to Philadelphia detectives
Prosecutors and law enforcement in the Delaware Valley say behind the scenes, investigators in Pima County, Arizona, are poring over data and tens of thousands of tips from members of the public in the search for Nancy Guthrie.
At recent high-profile trials in Philadelphia, prosecutors have taken down defendants, locking them up using data from their cellphones, combined with other physical evidence corroborating their presence at locations relevant to the case. The technology is critical, veteran prosecutors have said.
In court, accused killers and alleged mass shooters have been confronted by an avalanche of data brought by investigators: hours-long presentations made by homicide detectives showing defendants' movements from cell data paired with surveillance video and GPS from a variety of sources, including automatic license plate readers (ALPR).
Detectives apply for warrants and obtain information from so-called cellphone tower data dumps with surveillance video, proving near-exact location. The information is regularly used in court to show precisely where someone is and if their phone is on.
"We have our devices, and they're always communicating with cell towers," Joe Lanuti, an assistant chief of the Philadelphia District Attorney's Office Gun Violence Task Force, said. "Whenever I'm doing an investigation, we are always looking at what devices we can put at the scene of a crime."
During the intensive search for 23-year-old Kada Scott, who suddenly disappeared from her place of employment in early October, Philadelphia police testified at a hearing this month that they "back-tracked" the defendant's phone. They discovered his movements and exactly where he allegedly was.
A municipal court judge ruled there was sufficient evidence to send the case against Keon King to trial. Scott's partially decomposed remains were discovered in a wooded area behind a former middle school in East Germantown. Police used cellphone tower "dumps" to amass their case against King. Paired with video, the data revealed King's movements in the hours before and after Scott's death.
King is expected to plead not guilty at a formal arraignment next week.
"You get all the phones that were in that area," Vito Roselli, a retired FBI special agent, said.
Roselli added the ongoing work by investigators in the Guthrie case amounts to the proverbial search for a needle in a haystack. Processing all that data takes time, he said.
"You have to have somebody that's going through all those records and determining what are legitimate (phone) numbers? What numbers have or haven't been in the area before? You have to find patterns for numbers," Roselli said.
As investigators find leads and track down persons of interest or suspects, experts said cell data will be used to corroborate other important pieces of evidence.
"I always think of it as a tool, just like all our other tools like ballistics, or other forensics data," Lanuti said. "It's a layer upon which you can set upon other layers, like witness testimony, video evidence."
Experts said even with all the data, some of the highest-profile cases still benefited from "old school" tips called in from the public about what they saw.