What your cell phone can’t tell the police (The New Yorker, 26 June 2014) – On May 28th, Lisa Marie Roberts, of Portland, Oregon, was released from prison after serving nine and a half years for a murder she didn’t commit. A key piece of overturned evidence was cell-phone records that allegedly put her at the scene. Roberts pleaded guilty to manslaughter in 2004, after her court-appointed attorney persuaded her that she had no hope of acquittal. The state’s attorney had told him that phone records had put Roberts at the scene of the crime, and, to her lawyer, that was almost as damning as DNA. But he was wrong, as are many other attorneys, prosecutors, judges, and juries, who overestimate the precision of cell-phone location records. Rather than pinpoint a suspect’s whereabouts, cell-tower records can put someone within an area of several hundred square miles or, in a congested urban area, several square miles. Yet years of prosecutions and plea bargains have been based on a misunderstanding of how cell networks operate. No one knows how often this occurs, but each year police make more than a million requests for cell-phone records. “We think the whole paradigm is absolutely flawed at every level, and shouldn’t be used in the courtroom,” Michael Cherry, the C.E.O. of Cherry Biometrics, a consulting firm in Falls Church, Virginia, told me. “This whole thing is junk science, a farce.” The paradigm is the assumption that, when you make a call on your cell phone, it automatically routes to the nearest cell tower, and that by capturing those records police can determine where you made a call-and thus where you were-at a particular time. That, he explained, is not how the system works. When you hit “send” on your cell phone, a complicated series of events takes place that is governed by algorithms and proprietary software, not just by the location of the cell tower. First, your cell phone sends out a radio-frequency signal to the towers within a radius of up to roughly twenty miles-or fewer, in urban areas-depending on the topography and atmospheric conditions.
Provided by MIRLN.
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