State v. Pratt

Leo Pratt (defendant) was charged with sexually abusing his 12-year-old niece. At trial, the State of Vermont (plaintiff) introduced evidence that Pratt’s cell phone had linked to pornographic websites. The state recovered the information from Pratt’s phone using software called Cellebrite. The state presented testimony from a forensic expert about how he used Cellebrite to extract the data from Pratt’s phone. The expert testified that he had over 800 hours of training in examining computer hard drives, digital media, and cell phones. He also testified that he had one week of training specifically on Cellebrite and had used Cellebrite to extract data from hundreds of cell phones. The expert explained that although he was unable to testify specifically about how the underlying programming for the Cellebrite software worked, he had read articles about the software and its capabilities. The expert also testified that he did not know Cellebrite’s error rate, but his training had included a discussion of Cellebrite’s limitations. He also testified that Cellebrite is the most popular software for examining cell phones, that Cellebrite and its results are regularly tested by experts and subject to peer review, and that the software is considered reliable in the forensic-examination industry. The expert also explained that he self-tests his own Cellebrite data-extraction results by comparing them with results from other data-extraction tools and with a manual examination of the cell phone. Pratt was convicted, and he appealed to the Vermont Supreme Court. One of Pratt’s arguments on appeal was that the trial court erred in admitting the forensic expert’s testimony. Pratt argued that the expert did not understand the programming underlying the Cellebrite software and that the expert’s testimony did not sufficiently establish Cellebrite’s reliability.