Someone strangled a prostitute in Portland, Oregon in 2002. The police arrested Lisa Roberts, the victim's ex-lover, who spent more than two years in custody awaiting trial. Shortly before the trial the prosecutor told Ms Roberts, via her lawyer, that tower data collected by Verizon, her mobile-telephone network, showed precisely where she was at the time of the murder. As her lawyer recalled, the prosecutor said Ms Roberts could be "pinpointed" in a park shortly before the victim's naked and sexually assaulted corpse was found there. She was told she faced 25 years to life in prison. She accepted a deal to plead guilty and serve 15 years. But the high-tech evidence against her was bunk. Routinely collected tower data can place a mobile phone in a broad area, but it cannot "pinpoint" it. That would require a special three-tower "triangulation", which cannot reveal past locations. It took a decade for Ms Roberts's guilty plea to be thrown out. On May 28th she left prison, her criminal record clean, after nearly 12 years in custody.
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