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Cellular Carrier Handset Location & Call Detail Records Error Rates Overview

 

By John B. Minor, CSA CCE CSE, Communications Expert

All Rights Reserved – Copyright 2012

 

 

John B. Minor was awarded a patent for a new methodology related to error mitigation and validation of cellular carrier records during the analysis and mapping of these records. See Google link

Twenty three year old Larissa Cavazos was found beaten and shot to death in her Edinburgh, Texas apartment on December 1st, 2005. Detectives determined that Larissa’s cell phone had been removed from the crime scene and immediately declared an exigent circumstance requesting that Sprint initiate live locate requests for the handset. Larissa’s handset responded with location information yet detectives never found the handset.

In 2009, the author was hired by the Hidalgo County District Attorney as communications expert in the investigation and prosecution of Lozano Quintanilla. Paul Taylor, Sprint Nextel Wiretap Surveillance / Location Based Services Department manager, was contacted to ascertain the location determination techniques used by Sprint Nextel in 2005. During discussions with Mr. Taylor it was learned that the location determination techniques currently in use were the same techniques used in December 2005.

The resulting location “pings” placed Larissa’s handset in the vicinity of the home of Quintanilla within an accuracy radius of 15-21 meters. The margin of error for the location responses became instrumental in obtaining a conviction in this case and Mr. Quintanilla is serving a life sentence.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sprint Live Tracking Portal (upper left of graphic) – Location Tracking Result (upper right)

Experts are typically challenged regarding error rates associated with evidence analysis and render opinions during testimony. Cellular carriers have not willingly revealed any error rate information to the public, leaving experts to validate the accuracy of carrier records produced and used as evidence.

Statistical data regarding cellular carrier records error rates is scant and has not been adequately developed and studied. This article presents actual evidence characterizing errors in cell phone records production and analysis discovered to date.

Background

The role of Cellular Carrier Location Based Services in civil and criminal litigation is growing at an exponential rate. Law enforcement investigators and key communications experts within the technology & communications industry have been engaged as cellular handset geo-location analysts with ever greater frequency as interest in using device position determination evidence in civil and criminal litigation has grown. Some experts have recognized that information production by cellular carriers must be carefully validated rather than accepted as factual.

Communications technologies error rates are readily determined and presented for virtually every type of communications activity. The most common communications record in use in courtrooms today is the cellular carrier Call Detail Record (CDR). Despite this fact, the actual or statistical error rate for cellular carrier records production is notably absent. In fact, the location information provided within CDR’s is accepted without validation in most cases. No known error rates have been published for any cellular carrier location information production.

Cellular carrier networks in the United States implemented Location Based Services (LBS) for the purpose of geo-locating cell phone handsets both during active and idle communications modes primarily as a means of meeting government E911 requirements but also to enhance carrier revenue from the subscriber base.

 

The government mandate for Enhanced 911 hyperbolic ranging techniques initiated development and installation of LBS as early as 1998 as part of the required implementation of Phase I.

 

During Phase 2 hyperbolic ranging accuracy was enhanced and by 2005 over 95% of cell phone handsets were capable of position determination within 50 to 300 meters. Cell phones containing GPS chipsets are capable of location resolution of 5 to 30 meters.

 

During active and idle communications mode location queries, the LBS system attempts to perform hyperbolic ranging at high accuracy levels. As an example, Sprint Nextel's basis for subscriber number usage reporting, the Sprint Nextel subscriber billing system, was augmented with the E911 initiative (Location Based Services) to provide subscriber handset geo-location information beginning with Phase 1 in 1998. Sprint Nextel was entering Phase 2 in December 2001 in Rhode Island and by February 2004 Sprint Nextel had implemented Phase 2 in 24 states while attempting to meet a deadline date of year-end 2005. Other major cellular carriers including AT&T, T-Mobile and Verizon followed a similar course in efforts to meet E911 mandates. Sprint Nextel, Alltel and U.S. Cellular missed the year-end 2005 deadline and were fined by the Federal Communications Commission. All carriers today are thought to be in compliance with the E911 mandate, however, validation of compliance is an ongoing FCC requirement.

 

High accuracy level multilateration or trilateration cellular handset position determination techniques which include Advanced or Enhanced Forward Link Trilateration, Angle of Arrival, Time Difference of Arrival, Assisted-GPS and other techniques are employed, reverting to less accurate methods until a satisfactory certainty of geo-location determination has occurred were implemented by cellular carriers during E911 Phase 2. All carriers today are required to meet E911 Phase 2 location accuracy of 50 to 300 meters and thereby utilize one or more of the above LBS technologies during E911 calls, exigent circumstance locate requests or live handset tracking by law enforcement.

 

The least accurate geo-location method for LBS is the determination of cell site & sector (Cell-ID) within which the cell phone handset is communicating. During normal voice communications and absent E911 calls or law enforcement real-time tracking activity, a cell phone handset geo-location may only be determined by this least accurate Cell-ID method.

Beginning as early as the mid-1990’s, cellular carrier records, often today characterized as Call Detail Records (CDR’s), were obtained by law enforcement under the Communications Assistance for Law Enforcement Act (CALEA-1994). The CDR’s were utilized in important criminal investigations such as homicides, high value thefts/robberies or organized criminal activities to determine the approximate location of a suspects cell phone handset before and during the course of events. Early use of this information proved to be very successful in achieving a high conviction rate.

Law enforcement specialists were trained by cellular carriers to interpret the records and little, if any, due diligence was exercised to achieve verification of information produced by the carriers.

Since 2006 the number criminal and civil cases within which CDR’s have been utilized has skyrocketed and cellular carriers have continued to expand and enhance records custodian departments in an effort keep pace with the growing demand for such information.

Live multilateration and trilateration handset location calculation techniques, although rarely encountered, often include a margin of uncertainty. This type of evidence is typically found only in murder cases and the margin of uncertainty is the only error rate information produced by cellular carriers in real time handset tracking.

During the past several years this author has encountered numerous areas of cellular carrier records production in which obfuscation of location data or faulty location data was determined to be a critical issue in a civil or criminal case. In some cases the errors simply invalidated the cellular carrier records production. More often, time and cost constraints have prevented full validation of questionable carrier records.

The current absence of statistical data regarding cellular carrier records production error rates coupled with the urgency to characterize the types of errors encountered prompted this overview of a growing sense of fallibility in the cellular industry’s records keeping.

Categorization of the Types of Evidence Production or Analysis Errors Encountered

Errors have been discovered during cellular carrier evidence production reviews in several distinct areas:

Cellular Carrier Base Transceiver Station Location Database

Location Based Services Handset Geo-Location

Cellular Carrier Call Detail Records

Federal Communications Commission Universal Licensing Filings

Documented Network Infrastructure Failures & Communications Protocols

…… continued

 

The Complete Article is available ….