IEEE Technology and Society Magazine - June 2017 - 77

This result is compatible with the 1/8 efficacy expected for a useless device, and is incompatible with even
a moderately effective working one.

Investigating the GT200
The GT200 is claimed by its manufacturer, U.K.-based
Global Technical Ltd, to be a remote substance detector
that may identify numerous substances in quantities as
small as picograms and from distances as large as
5 km [1]. Documents obtained through the Mexican Federal Access to Information Institute (Instituto Federal de
Acceso a la Información, (IFAI)), and from the web portals of several government agencies [2], [3] show that
the Mexican Government bought more than 940 of
these devices at prices from $280 000MX to $580 000MX
mexican pesos each (the exchange rate fluctuated
around $13MX to $1USD). Its main users were the Mexican Army and Navy, with more than 742 and 102 units,
respectively, followed by the state petroleum company
with 54 units. According to press releases [4], the
GT200 was used successfully as a tool in the war
against drugs, in hundreds of searches for cocaine,
marijuana, etc. It was used at military checkpoints and
at airports and justified house searches and detentions
of an unknown number of citizens for presumed possession and trafficking of illegal substances. Nevertheless, the GT200 is one of a class of detectors based on
dowsing rods with brand names such as Quadro Tracker, DKL-Lifeguard, Mole, Sniffex, and ADE651, which
have invariably failed in controlled experiments1 (see
[5], and references therein).
W.Luis Mochán (WLM) participated as expert witness
in a judicial trial where the GT200 provided multiple
instances of evidence of drug and munition possession.
Its operators included the "theory of operation of the
apparatus" [6] in their statements, claiming it is sensitive
to characteristic "diamagnetic and paramagnetic fields"
produced by all substances, allowing their detection
and identification, and that it is programmed through
cards that are fed by "electrostatic energy" produced by
its operators, among many other statements filled with
pseudo-scientific jargon. WLM, asked to provide a
detailed criticism of this theory [7], concluded that "it
contains numerous conceptual errors and meaningless
statements that use scientific language but out of

1
See for example the following newspaper issues: Excélsior (Feb. 21,
2010); AM (Jul. 10, 2010); MVS News (Jul. 20, 2010); El Fronterizo (Jul.
21, 2010); Milenio, (Jul. 21, 2010); El Correo de Manzanillo, (Jul. 22,
2010); AM (Jul. 25, 2010); Milenio (Jul. 27, 2010); Proceso (Jul. 28, 2010);
El Universal (Jul. 29, 2010); El Pueblo (Aug. 2, 2010); AF Medios (Aug. 3,
2010); Correo de Manzanillo (Aug. 10, 2010), Eje Central (Apr. 28, 2011);
Cuarto Poder (Apr. 30, 2011); El Universal (May 6, 2011); Debate.com.mx
(May 8, 2011); El Sol de Mazatlán (May 9, 2011); AngelGuardianMX (May
12, (2011); ElEditorial.mx (May 13, 2011); Radio Trece (Jun. 5, 2011); La
Prensa (Jun. 7, 2011); Debate.com.mx (Jun. 26, 2011); Cuarto Poder (Jun.
30, 2011); Correo Guanajuato (Jul. 1, 2011).

june 2017

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context" and that "it is certain that the equipment is
useless." This study was used in a different judicial trial
in which the judge Karla Macías Lovera released Ernesto
Cayetano, a man who had been accused of drug trafficking [8] and thus spent 8 months in jail. It has also
been discussed within the Mexican Senate [9], [10],
which exhorted the President of Mexico to order the scientific evaluation of the efficacy of the GT200 [11].
Alejandro Ramírez (AR) participated as expert witness in another trial and was asked to determine the
validity of the evidence provided by the GT200. The
judge ordered the Army to provide a GT200 apparatus,
an expert operator, enough quantity of a detectable
substance and to participate in a test to be conducted
by AR. Curiously, Arturo Menchaca, former president of
the Mexican Academy of Science (Academia Mexicana
de Ciencias, AMC) had offered help for testing the
device; it was rejected so as not to violate the terms of
the purchase contract (fragments of the corresponding
letters are displayed in [9]). The test, conducted by AR
and WLM, was carried out on October 21, 2011, on the
grounds of the AMC. Being part of a trial in progress,
the results were not released at once. Nevertheless,
about a year after the test, the trial showed no progress
and the main results were published by a national newspaper [12].
The purpose of this article is to describe the test and
its results.

Test
We wrote down a meticulously detailed protocol, trying
to make it as unambiguous as feasible. We wanted our
results to be clear cut about the effectiveness of the
detector and we wanted to avoid any kind of extraneous
explanations and excuses beyond the ineffectiveness of
the device, were it to fail the test. A description of the
protocol and details of the test may be found in [13],
and an anecdotal account in [14], [15]. Here we give a
summary of the test.
The device was tested on Oct. 21, 2011, at an abandoned 90-m × 20-m ballroom within the grounds of the
AMC (which occupy a palace built for a former police
chief and later confiscated by the government). The
sample to be searched consisted of 1630 30-mg capsules of Itrabil and 33 30-mg capsules of Obeclox, both
with the substance Clorobenzorex, a stimulant drug of
the phenethylamine and amphetamine chemical families. The rest of the sample consisted of 3 9-mm ×
19-mm bullets and one 0.28-in (7.1-mm) bullet. The
sample had presumably been detected using the GT200
and later confiscated from the house of Juanita
Velázquez, defendant in the trial for which the experiment was ordered. Two policemen and two members of
the army were in charge of safeguarding the sample but

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