Assessing Advanced Cellphone Location Evidence

By: Nathan Oswald​​
Featured in Ohio Lawyer, Vol. 31, No. 6 (reprinted with permission)

Your cellphone thinks it knows where you are. Even when the GPS is off.

In recent years, all the major cellular providers have developed advanced technology that purports to determine the approximate locations of cellphones on the providers' networks, even without GPS. Law enforcement has been especially interested in this technology for locating a cellphone before, during, or after a crime. It offers the same promise in civil cases. Because this evidence is the product of complicated technological processes, jurors may be tempted to believe that the processes are infallible.

The Ohio Rules of Evidence requires that evidence like this meet certain minimum standards. Rule 702(C) sets threshold criteria that the proponent must satisfy for the admission of evidence derived from novel scientific or technical processes.

A brief overview of advanced cellphone location technology

Verizon's latest technology for locating cellphones on its network is called RTT (Round Trip Time). Sprint has PCMD (Per Call Measurement Data), and AT&T developed NELOS (Network Event Location System). This article focuses on NELOS as an example of the recent inventions.

According to AT&T's patents, NELOS relies on the time it takes electromagnetic pulses to travel between a cellphone and nearby cellular towers to determine a cellphone's distance from the towers—optimally to within 25 meters. But the rate at which electromagnetic radiation travelsthe speed of light in a vacuum​is delayed somewhat in the real world by factors unrelated to distance. These factors include the user's cellphone, components of the communications network, the atmosphere, physical obstructions, etc.

The reliability of the NELOS procedure depends on the validity of AT&T's algorithms and the accuracy of how they adjust for the fact​ors other than distance that affect the travel time of network data.

Rule 702(C) sets threshold criteria for novel technological processes

Ohio Evidence Rule 702(C) states three elements for admitting results of scientific or technological procedures. Litigants who challenge the reliability of cellphone location technologies have a framework in this rule for evaluating evidence created by these procedures.

1. The theory must be objectively verifiable or validly derived from widely accepted knowledge, facts, or principles.

NELOS is protected by several patents. But a patent is no indication that the invention it describes is scientifically valid or technologically achievable. For example, patent #8,224,349 refers to undisclosed algorithms that calculate time differentials of electromagnetic pulses.1 Nothing in that patent reveals the kind of detail that a peer would need to test or to verify the algorithms.

Just as importantly, some of the patents acknowledge possible errors that "can be associated with various measurements involved in the disclosed calculations."2 Those errors can purportedly "be addressed by well-known statistical methods for sufficiently large sets of location data."3 But the patents fail to disclose either the statistical methods or how data sets are selected. More fundamentally, the proposition that data can be leveraged to correct timing errors requires validation. Bald assertions like these may be adequate for the Patent Office, but they don't suffice for Rule 702. In G.E. v. Joiner, the U.S. Supreme Court admonished courts against relying on conclusory assurances when applying Evidence Rule 702.4 Unless the proponent of NELOS evidence can demonstrate that the algorithms are in fact either "objectively verifiable or validly derived from widely accepted knowledge, facts, or principles," a court has no basis for finding that the technology satisfies Rule 702(C)(1).

2. The procedure must reliably implement the theory.

To determine unknown distances between a cellphone and nearby towers, technology must account for variables that affect electromagnetic pulses that transmit over unknown distances. Some of these are intrinsic to the NELOS system; others are external. "Timing delay typically is caused by various source[s], e.g., mismatches among electronic elements and components (e.g., impedance mismatch), stray capacitances and inductances, length of the antenna(s) cable(s) in base station(s); tower height of base station, . . . signal path scattering, . . . strong reflections, etc."5

The patents acknowledge that NELOS sometimes fails to adjust for timing delay. "[T]iming and delay errors can be compensated for where the errors in delay and timing can be determined."6 Also, different amounts of data may be available in different areas and that disparity can impact the technology's ability to correct for the delays.7 Further, the technology assumes, without any justification stated in the patents, that "cell site delay" "is relatively stable over periods of hours to days."8 All of these unverified assumptions and unanswered questions about how the theory was implemented provide grounds for a court to exclude the results of cellphone location technology pursuant to Rule 702(C)(2).

3. The procedure must be conducted in a way that will yield accurate results.

NELOS has evolved even in the few years it has existed. The patents reveal a string of refinements. This implies, of course, that improvements were needed.

Lawyers facing cellphone location evidence should always investigate the reliability of the version of the technology used on the day in question. Subsequent revisions might mean that a problem affected the prior version's reliability. The proponent has the burden under Rule 702(C)(3) of demonstrating that the technology as it was implemented adhered to the patents that describe its functionality.

Follow the Rule

Evidence Rule 702(C) provides a framework for lawyers and courts to assess whether cellular providers' novel inventions are reliable enough to be admissible in evidence. Rule 702(C) provides the template for assessing the reliability of novel procedures, tests and experiments. In the area of cellphone location technology, these processes are becoming ever more common.

Endnotes

1 Cols. 13, 13-21; 14, 24-40.
2 #8,224,349 col. 9, 21-24.
3 #8,494,557 col. 9, 36-37; #8,886,219 col. 9, 27-29.
4 522 U.S. 136, 146 (1997).
5 #8,224,349 col. 6, 60–7, 5.
6 #8,224,349 col. 7, 6-8.
7 #8,494,557 col. 7, 21-24.
8 #8,224,349 col. 9, 6-7; #8,494,557 col. 7, 7-8.

The materials available at this web site are for informational purposes only and not for the purpose of providing legal advice. You should contact your attorney to obtain advice with respect to any particular issue or problem. Use of and access to this web site or any of the links contained within the site do not create an attorney-client relationship between Thacker Robinson Zinz LPA and the user or browser. The opinions expressed at or through this site are the opinions of the individual author and may not reflect the opinions of the firm or any individual attorney.

Back to posts
Print article

Assessing Advanced Cellphone Location Evidence

By: Nathan Oswald​​
Featured in Ohio Lawyer, Vol. 31, No. 6 (reprinted with permission)

Your cellphone thinks it knows where you are. Even when the GPS is off.

In recent years, all the major cellular providers have developed advanced technology that purports to determine the approximate locations of cellphones on the providers' networks, even without GPS. Law enforcement has been especially interested in this technology for locating a cellphone before, during, or after a crime. It offers the same promise in civil cases. Because this evidence is the product of complicated technological processes, jurors may be tempted to believe that the processes are infallible.

The Ohio Rules of Evidence requires that evidence like this meet certain minimum standards. Rule 702(C) sets threshold criteria that the proponent must satisfy for the admission of evidence derived from novel scientific or technical processes.

A brief overview of advanced cellphone location technology

Verizon's latest technology for locating cellphones on its network is called RTT (Round Trip Time). Sprint has PCMD (Per Call Measurement Data), and AT&T developed NELOS (Network Event Location System). This article focuses on NELOS as an example of the recent inventions.

According to AT&T's patents, NELOS relies on the time it takes electromagnetic pulses to travel between a cellphone and nearby cellular towers to determine a cellphone's distance from the towers—optimally to within 25 meters. But the rate at which electromagnetic radiation travelsthe speed of light in a vacuum​is delayed somewhat in the real world by factors unrelated to distance. These factors include the user's cellphone, components of the communications network, the atmosphere, physical obstructions, etc.

The reliability of the NELOS procedure depends on the validity of AT&T's algorithms and the accuracy of how they adjust for the fact​ors other than distance that affect the travel time of network data.

Rule 702(C) sets threshold criteria for novel technological processes

Ohio Evidence Rule 702(C) states three elements for admitting results of scientific or technological procedures. Litigants who challenge the reliability of cellphone location technologies have a framework in this rule for evaluating evidence created by these procedures.

1. The theory must be objectively verifiable or validly derived from widely accepted knowledge, facts, or principles.

NELOS is protected by several patents. But a patent is no indication that the invention it describes is scientifically valid or technologically achievable. For example, patent #8,224,349 refers to undisclosed algorithms that calculate time differentials of electromagnetic pulses.1 Nothing in that patent reveals the kind of detail that a peer would need to test or to verify the algorithms.

Just as importantly, some of the patents acknowledge possible errors that "can be associated with various measurements involved in the disclosed calculations."2 Those errors can purportedly "be addressed by well-known statistical methods for sufficiently large sets of location data."3 But the patents fail to disclose either the statistical methods or how data sets are selected. More fundamentally, the proposition that data can be leveraged to correct timing errors requires validation. Bald assertions like these may be adequate for the Patent Office, but they don't suffice for Rule 702. In G.E. v. Joiner, the U.S. Supreme Court admonished courts against relying on conclusory assurances when applying Evidence Rule 702.4 Unless the proponent of NELOS evidence can demonstrate that the algorithms are in fact either "objectively verifiable or validly derived from widely accepted knowledge, facts, or principles," a court has no basis for finding that the technology satisfies Rule 702(C)(1).

2. The procedure must reliably implement the theory.

To determine unknown distances between a cellphone and nearby towers, technology must account for variables that affect electromagnetic pulses that transmit over unknown distances. Some of these are intrinsic to the NELOS system; others are external. "Timing delay typically is caused by various source[s], e.g., mismatches among electronic elements and components (e.g., impedance mismatch), stray capacitances and inductances, length of the antenna(s) cable(s) in base station(s); tower height of base station, . . . signal path scattering, . . . strong reflections, etc."5

The patents acknowledge that NELOS sometimes fails to adjust for timing delay. "[T]iming and delay errors can be compensated for where the errors in delay and timing can be determined."6 Also, different amounts of data may be available in different areas and that disparity can impact the technology's ability to correct for the delays.7 Further, the technology assumes, without any justification stated in the patents, that "cell site delay" "is relatively stable over periods of hours to days."8 All of these unverified assumptions and unanswered questions about how the theory was implemented provide grounds for a court to exclude the results of cellphone location technology pursuant to Rule 702(C)(2).

3. The procedure must be conducted in a way that will yield accurate results.

NELOS has evolved even in the few years it has existed. The patents reveal a string of refinements. This implies, of course, that improvements were needed.

Lawyers facing cellphone location evidence should always investigate the reliability of the version of the technology used on the day in question. Subsequent revisions might mean that a problem affected the prior version's reliability. The proponent has the burden under Rule 702(C)(3) of demonstrating that the technology as it was implemented adhered to the patents that describe its functionality.

Follow the Rule

Evidence Rule 702(C) provides a framework for lawyers and courts to assess whether cellular providers' novel inventions are reliable enough to be admissible in evidence. Rule 702(C) provides the template for assessing the reliability of novel procedures, tests and experiments. In the area of cellphone location technology, these processes are becoming ever more common.

Endnotes

1 Cols. 13, 13-21; 14, 24-40.
2 #8,224,349 col. 9, 21-24.
3 #8,494,557 col. 9, 36-37; #8,886,219 col. 9, 27-29.
4 522 U.S. 136, 146 (1997).
5 #8,224,349 col. 6, 60–7, 5.
6 #8,224,349 col. 7, 6-8.
7 #8,494,557 col. 7, 21-24.
8 #8,224,349 col. 9, 6-7; #8,494,557 col. 7, 7-8.

The materials available at this web site are for informational purposes only and not for the purpose of providing legal advice. You should contact your attorney to obtain advice with respect to any particular issue or problem. Use of and access to this web site or any of the links contained within the site do not create an attorney-client relationship between Thacker Robinson Zinz LPA and the user or browser. The opinions expressed at or through this site are the opinions of the individual author and may not reflect the opinions of the firm or any individual attorney.

Back to posts
Print article

Assessing Advanced Cellphone Location Evidence

By: Nathan Oswald​​
Featured in Ohio Lawyer, Vol. 31, No. 6 (reprinted with permission)

Your cellphone thinks it knows where you are. Even when the GPS is off.

In recent years, all the major cellular providers have developed advanced technology that purports to determine the approximate locations of cellphones on the providers' networks, even without GPS. Law enforcement has been especially interested in this technology for locating a cellphone before, during, or after a crime. It offers the same promise in civil cases. Because this evidence is the product of complicated technological processes, jurors may be tempted to believe that the processes are infallible.

The Ohio Rules of Evidence requires that evidence like this meet certain minimum standards. Rule 702(C) sets threshold criteria that the proponent must satisfy for the admission of evidence derived from novel scientific or technical processes.

A brief overview of advanced cellphone location technology

Verizon's latest technology for locating cellphones on its network is called RTT (Round Trip Time). Sprint has PCMD (Per Call Measurement Data), and AT&T developed NELOS (Network Event Location System). This article focuses on NELOS as an example of the recent inventions.

According to AT&T's patents, NELOS relies on the time it takes electromagnetic pulses to travel between a cellphone and nearby cellular towers to determine a cellphone's distance from the towers—optimally to within 25 meters. But the rate at which electromagnetic radiation travelsthe speed of light in a vacuum​is delayed somewhat in the real world by factors unrelated to distance. These factors include the user's cellphone, components of the communications network, the atmosphere, physical obstructions, etc.

The reliability of the NELOS procedure depends on the validity of AT&T's algorithms and the accuracy of how they adjust for the fact​ors other than distance that affect the travel time of network data.

Rule 702(C) sets threshold criteria for novel technological processes

Ohio Evidence Rule 702(C) states three elements for admitting results of scientific or technological procedures. Litigants who challenge the reliability of cellphone location technologies have a framework in this rule for evaluating evidence created by these procedures.

1. The theory must be objectively verifiable or validly derived from widely accepted knowledge, facts, or principles.

NELOS is protected by several patents. But a patent is no indication that the invention it describes is scientifically valid or technologically achievable. For example, patent #8,224,349 refers to undisclosed algorithms that calculate time differentials of electromagnetic pulses.1 Nothing in that patent reveals the kind of detail that a peer would need to test or to verify the algorithms.

Just as importantly, some of the patents acknowledge possible errors that "can be associated with various measurements involved in the disclosed calculations."2 Those errors can purportedly "be addressed by well-known statistical methods for sufficiently large sets of location data."3 But the patents fail to disclose either the statistical methods or how data sets are selected. More fundamentally, the proposition that data can be leveraged to correct timing errors requires validation. Bald assertions like these may be adequate for the Patent Office, but they don't suffice for Rule 702. In G.E. v. Joiner, the U.S. Supreme Court admonished courts against relying on conclusory assurances when applying Evidence Rule 702.4 Unless the proponent of NELOS evidence can demonstrate that the algorithms are in fact either "objectively verifiable or validly derived from widely accepted knowledge, facts, or principles," a court has no basis for finding that the technology satisfies Rule 702(C)(1).

2. The procedure must reliably implement the theory.

To determine unknown distances between a cellphone and nearby towers, technology must account for variables that affect electromagnetic pulses that transmit over unknown distances. Some of these are intrinsic to the NELOS system; others are external. "Timing delay typically is caused by various source[s], e.g., mismatches among electronic elements and components (e.g., impedance mismatch), stray capacitances and inductances, length of the antenna(s) cable(s) in base station(s); tower height of base station, . . . signal path scattering, . . . strong reflections, etc."5

The patents acknowledge that NELOS sometimes fails to adjust for timing delay. "[T]iming and delay errors can be compensated for where the errors in delay and timing can be determined."6 Also, different amounts of data may be available in different areas and that disparity can impact the technology's ability to correct for the delays.7 Further, the technology assumes, without any justification stated in the patents, that "cell site delay" "is relatively stable over periods of hours to days."8 All of these unverified assumptions and unanswered questions about how the theory was implemented provide grounds for a court to exclude the results of cellphone location technology pursuant to Rule 702(C)(2).

3. The procedure must be conducted in a way that will yield accurate results.

NELOS has evolved even in the few years it has existed. The patents reveal a string of refinements. This implies, of course, that improvements were needed.

Lawyers facing cellphone location evidence should always investigate the reliability of the version of the technology used on the day in question. Subsequent revisions might mean that a problem affected the prior version's reliability. The proponent has the burden under Rule 702(C)(3) of demonstrating that the technology as it was implemented adhered to the patents that describe its functionality.

Follow the Rule

Evidence Rule 702(C) provides a framework for lawyers and courts to assess whether cellular providers' novel inventions are reliable enough to be admissible in evidence. Rule 702(C) provides the template for assessing the reliability of novel procedures, tests and experiments. In the area of cellphone location technology, these processes are becoming ever more common.

Endnotes

1 Cols. 13, 13-21; 14, 24-40.
2 #8,224,349 col. 9, 21-24.
3 #8,494,557 col. 9, 36-37; #8,886,219 col. 9, 27-29.
4 522 U.S. 136, 146 (1997).
5 #8,224,349 col. 6, 60–7, 5.
6 #8,224,349 col. 7, 6-8.
7 #8,494,557 col. 7, 21-24.
8 #8,224,349 col. 9, 6-7; #8,494,557 col. 7, 7-8.

The materials available at this web site are for informational purposes only and not for the purpose of providing legal advice. You should contact your attorney to obtain advice with respect to any particular issue or problem. Use of and access to this web site or any of the links contained within the site do not create an attorney-client relationship between Thacker Robinson Zinz LPA and the user or browser. The opinions expressed at or through this site are the opinions of the individual author and may not reflect the opinions of the firm or any individual attorney.

Back to posts
Print article

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