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The "known" is the original calibration of the instrument

Updated: Sep 9, 2022


To separate the concepts of "calibration" from "control checks"

To clarify that "calibration" is something that happens at the factory, not at time of use by a qualified technician

To clarify that control tests at time of testing are simply a verification (to use the CFS scientist's words) that calibration hasn't changed over time (note Hodgson concept of "over time" in his paper referred to in St-Onge)

Sample Cross-examination on clarification by CFS expert as to why previous subject tests are irrelevant. Confronted CFS expert that it is the "knowns" that are relevant and the "knowns", the reference standards, are at the time of calibration at the factory - not the control test. Prior subject tests may be irrelevant but connection of the instrument at time of use to the "known" is essential to reliability.

[I will suggest in another part of the cross-examination that single value control tests of 100 mg/100 mls are totally inadequate to verify calibration of the instrument across the measuring interval of the instrument.}

The known kilogram, for example, (until mid-2018) was a physical artifact in France. All other kilograms internationally were traceable to that kilogram. Any measurement in Canada, by virtue of section 4(1) of our Weights and Measures Act must be traceable back to the Canadian knowns (the reference standards) at the National Research Council which in turn were traceable to the international prototypes such as the kg prototype pictured below.

Q. Yes.

A. When I say that each test is separate and

independent, the result that's obtained is separate and

independent, because, of course, the individual who provided

the sample is one individual who provided a sample of a

particular quality into the instrument that produced a

response that we know of and that produced that result, and

then another test is produced at another time, again,

separate and independent from that, that also produces a

result that may or may not be the same as the first result,

depending on the quality of the sample that's produced. And,

of course, that individual has two separate results, and

it's, again, different from other subjects who provide

samples as well, because we don't know what the alcohol is

that's in their system, and so that's what the device is

measuring. And so it's separate and independent in that way,

that that subject is completely different from the subject

who was tested in this case.

Q. I see. So as Mr. Kupferschmidt said, we

always proceed from knowns to unknowns. We have an unknown

that comes into the sample chamber in the instrument, but we

have a known, and the known is the calibration of the


A. Yes.

Q. Not the control checks, the known is the

calibration of the instrument?

A. Yes. The calibration checks done at the time

of testing is just to verify that the calibration hasn't

changed since that period in time.

For the very highly motivated, please watch (and explain to me):

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