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When a mobile device connects to a cell site, the mobile carrier often records the activity ( i.e., a sent text message), the time of the activity, and the location of the cell site and sector that was used. To illustrate this point, Picture 1 is an overview picture of a multi-directional cell tower.
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In North America, many cell towers contain three sets of antennas, with each set offering specific coverage area. When CDRs include cell site location data, analysts and law enforcement officers use these records to show the location of the cell site and the orientation of the sector. This article provides an overview of CSLI and NELOS records, discusses the order excluding NELOS records from trial, and provides practical advice for practitioners. However, after a Daubert hearing where the CAST agent testified, the district court excluded the records, in part, because of concerns over the reliability of the algorithms used to determine the location data. In a recent federal case, the government, through a member of the Federal Bureau of Investigation’s (“FBI”) Cellular Analysis Survey Team (“CAST”), sought to introduce NELOS records in a trial. This location data is derived from proprietary algorithms. In AT&T parlance, such records are based on the Network Event Location System (“NELOS”). Recent technological improvements have resulted in mobile carriers now generating Enhanced Location Records (“ELRs”), which purport to show more precise location data. For these purposes, it is important to keep in mind that the records only show the location of the cell site and the direction the antenna is facing. At times, the records generated by mobile carriers include the location of the cell site or cell sites and the direction of antenna that connected with the mobile device.Ĭell Site Location Information (“CSLI”) is the practice of creating maps showing the possible coverage area of a cell site at the time a device was being used. These records are called Usage Detail Records (“UDRs”). Mobile carriers likewise keep records of when data is used, such as browsing the internet. CDRs are generated when a mobile device sends or receives calls and text messages. The records are called Call Detail Records (“CDRs”). For many years, law enforcement officers have used records generated by mobile carriers to place a mobile device in a general area.