Prosecutors’ use of mobile phone tracking is ‘junk science,’ critics say

ABA Journal

At his trial last year on federal kidnapping and conspiracy charges, prosecutors sought to introduce cell tower evidence purporting to show that calls placed from defendant Antonio Evans’ cellphone could have come from his aunt’s house, where the victim was thought to have been held for ransom.

That’s not unusual. Hardly a day goes by when some prosecutor doesn’t go to court armed with cell tower evidence he or she claims places a defendant in the vicinity of a crime the defendant is accused of committing.

What made the Evans case unusual was the fact that the defense even put up a fight to keep the cell tower evidence out of the trial. Evans’ lawyers said the technique has not been shown to be scientific.

Such testimony usually goes unchallenged, presumably because most defense lawyers either accept at face value prosecutors’ assurances that cell tower evidence is scientific or because they don’t know enough about the underlying technology to understand its limitations. And, on the few occasions that it has been challenged, the courts have always let it in.

Until U.S. District Judge Joan H. Lefkow of Chicago came along, that is. Lefkow, who tried the Evans case, took an in-depth look at the cell tower evidence the government was proposing to use and found it wanting. The judge wrote that “multiple factors can affect the signal strength of a tower” and an FBI special agent’s “chosen methodology has received no scrutiny outside the law enforcement community.” As a result, the court concluded that the government had not demonstrated that testimony was reliable, Lefkow wrote in an Aug. 29, 2012, opinion and order.

Critics of cell tower tracking, as the practice is often called, say the decision is long overdue. It marks the first partial defense victory against the use of such evidence on Daubert grounds, the test formulated in the 1993 U.S. Supreme Court case Daubert v. Merrell Dow Pharmaceuticals. The test says that the judge should rule on the admissibility of scientific information submitted to assist the fact finder. It is used by federal and many state courts to determine the admissibility of expert testimony. Critics hope the case represents a turning point in the courts’ general tendency to submit when dubious scientific techniques such as cell tower tracking are proffered.

Michael Cherry, the CEO of Cherry Biometrics, a Falls Church, Va.-based consulting firm that has led the legal assault on cell tower tracking, calls it “junk science” that should never be admitted in any court for any reason. In fact, he can’t believe that such an easily disproved technique, which has been around for a decade or more, is still routinely being used in court.

“No one who understands the relevant science would ever claim that data from a single cell tower can reliably be used to specify the location of a caller at the time a particular call is made,” he says.

But in 2011, the nation’s nine largest cellphone carriers responded to 1.3 million requests for subscriber information of all kinds, including cell tower records, from law enforcement officials, according to data compiled by a congressional committee.

Cell tower records, also known as call detail records, are the billing records cell companies use to keep track of their customers’ calls. They show the date and time of all calls made or received, the numbers called, the duration of each call, and the cell towers used to begin and end a call. And those requests have been rising at an annual rate of 12 percent to 16 percent in the past five years.

Edward J. Imwinkelried, a law professor at the University of California at Davis who co-authored a treatise on scientific evidence, says cell tower records are not completely worthless. But they’re nowhere near as probative as many police and prosecutors would like to think.

EVIDENTIARY LIMITS

The records can tell you whether a person who has denied being in the coverage area of a particular tower at a given time was lying, he says. But they can’t tell you where within that coverage area the caller was; in some areas, the caller could have been anywhere within a 420-square-mile vicinity of a particular tower.

“Some of what these people who are interpreting this data are saying they can do with it is just nonsense,” Imwinkelried says.

Imwinkelried, who last year co-wrote an article in Judicature magazine on the subject with Cherry and a handful of defense lawyers, says that cell tower records, unlike Global Positioning System technology, were never designed to be used for tracking purposes. But not all cellphones are equipped with GPS technology, which can pinpoint a caller’s location down to a radius of about 50 meters, leaving cell tower records the only way of tracking a phone without it.

Imwinkelried says he’s not surprised that cell tower evidence has survived as long as it has without being subjected to serious scientific scrutiny. He likens it to voiceprint identification evidence and comparative bullet lead-analysis evidence, two once-highly touted forensic techniques that were initially embraced by the courts but eventually discredited. [MORE]