Guilt by Mobile Phone Tracking Shouldn't Make ‘Evidence to the Contrary’ Impossible

91 Pages Posted: 3 Oct 2016 Last revised: 13 Oct 2016

Date Written: October 1, 2016


Mobile phone (cellphone) tracking evidence was critically important to a murder conviction. Such evidence will be among the most frequently used electronically-produced evidence of location. How does a defendant produce “evidence to the contrary” for purposes of challenging its reliability? Rare and very difficult it will be that a defendant might get access to the complex electronic systems involved, to search for such suspected evidence. The law does not provide sufficient opportunity to challenge the reliability of evidence obtained from large, complex electronic records management systems (ERMSs). The court decisions show an ignorance of such technology.

A mobile phone can be located at the time of a particular call by finding the mobile phone tower that directed the call to it or from it. In urban areas such tracking can be as precise as 50 meters between tower and phone. By court order, the police can obtain such information from the mobile phone service provider. But for a defendant to obtain similar access for expert examination of the ERMS that produced it would be nearly impossible.

The prosecutor disclosed the routine procedure by which such information is produced by non-expert employees who answer such requests hundreds of times each year. But such disclosure does not include descriptions of the service provider’s technology, its software, history of performance, and the national and industry standards applicable to its maintenance. That is how the reliability of such complex systems must be proved. Instead, the case law relies upon: (1) the routine observations of those who use the system or device, but have no expertise as to its technology and no accountability for its performance; and, (2) the fact of great frequency of use by many similar users. But in comparison, although many millions of people use motor vehicles that does not prove their reliability. Millions of vehicles have to be recalled each year because of imperfections in their manufacture even though theirs is a heavily government-regulated industry. Thus “guilt by electronic device” is quite possible because, in effect, the ERMS is granted a “presumption of regularity” that cannot be rebutted.

Keywords: Mobile phone tracking, evidence to the contrary, evidentiary burden, presumption of regularity, fair trial, disclosure, national standards for electronic records management, guilt by electronic device, software error rates, full answer and defence, Linux kernel, Canada Evidence Act, 72.34

Suggested Citation

Chasse, Ken, Guilt by Mobile Phone Tracking Shouldn't Make ‘Evidence to the Contrary’ Impossible (October 1, 2016). Available at SSRN: or

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