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  • Stephen Biss

Traceability of a Measurement Result


Purpose:

To educate the Court about the meaning of "traceability" in measurement science.

To obtain an admission that there is a relationship between the calibration certificate (Certificate of Calibration) from the factory and the reference standards used during the factory calibration.

To obtain an admission that there is a relationship between the calibration certificate from the factory and the scientific reliability of the measurement result at time of use.

To introduce the NIST Certificate for the reference standards used at the time of calibration at the factory.

Sample cross-examination on "traceability" - How can every test stand on its own if every measurement result is a comparison to the reference standards used at the time of calibration at the factory? Surely the calibration certificate from the factory is relevant to reliability of the measurement result:

Q. All right. Let's talk about the whole

question of traceability of a measurement result.

A. Okay.

Q. You understand what traceability of a

measurement result is? You understand what I'm talking

about?

A. Yes.

Q. All right. Now, as I understand it from

reading the Intoxilyzer 8000C training aid, that measurements

in Canada -- that was Exhibit No. 20. We had an excerpt from

the training aid. And in the training aid...

A. December 2013.

Q. ...2013. Page 16 of 238. I will just show

you my own copy to save you some time.

A. Hold on. I have a whole bunch. Let me see if

I can find it.

Q. This is page 16 of 238 in Exhibit 20.

A. Okay. I don't know why there's two copies,

but....

Q. Page 16 of 238.

A. Yes.

Q. Third paragraph down:

The units for all the measurements needed in

science technology in every day life are derived

from SI base units, derived units and from units

outside the SI.

[As read]

A. Correct.

Q. Okay?

A. We covered that the last day.

Q. And above that:

"In 1960, the General Conference on Weights and

Measures adopted the International System of

units."

With the international abbreviation SI?

A. Yes. Right.

Q. Now, how is it that a measurement result on an

Intoxilyzer 8000C can be traceable to the SI units? Why does

that happen?

A. The instrument is traceable to the standards

that were used to check its calibration.

Q. Really? So you're suggesting that

traceability goes through the control checks by the police

officers, as opposed to the calibration of the instrument by

the factory?

A. No, that's not what I said. It's traceable to

the standards that were used at the point of calibration.

They are the standards obtained from Guth, or another

supplier, who certifies those standards, and the result is

traceable back to those standards.

Q. So on one of the previous days I showed you a

certificate of calibration for this particular Intoxilyzer

8000C that said that the solutions that were used were from a

standard 1820, and you looked at that document, and I think

we may have a copy of it as an exhibit.

A. Yes.

Q. So the traceability of an Intoxilyzer 8000C

goes back through its calibration. Not its control checks,

but through its calibration, right?

A. Correct.

Q. Same if it is recalibrated, the traceability

goes through the standards that are used, the reference

standards. And I think "reference standard" is a technical

term.

A. Yes.

Q. The reference standards that are used at the

time of its recalibration.

A. Correct.

Q. But there's an added difficulty, and that is

that the reference standards that are used during

recalibration could be, say, 50 milligrams per 100 mills, 100

milligrams per 100 mills, 300 milligrams per 100 mills. My

question for you is, how on earth can a measurement result in

an Intoxilyzer 8000C providing a traceable measurement if we

are talking about indications on the instrument of

approximately 130 milligrams per 100 mills or 140 milligrams

per 100 mills, if the calibration of the instrument was based

on standards at 50, 100 and 300?

A. So I believe we covered this during the last

day. That the calibration of the instrument is fixed at the

time of the calibration procedure, and when it's done, either

by a qualified individual or by a manufacture or a designated

person, company that's able to do that?

A. You're doing a single point check of the

calibration of the instrument using the standard of 100

milligrams of alcohol in 100 millimetres of blood every time

you check the instrument to see if it's working, in proper

working order. That standard determines that the

instrument -- the accuracy of the instrument, so basically is

it able to produce an accurate result. It shows that the

instrument is properly working, and that it hasn't lost its

calibration since the last time it was calibrated.

Q. All right. Again, I want to suggest to you

you're speaking policy, rather than science. My question to

you is, how is a measurement of approximately 130 or

approximately 140 milligrams per 100 mills, on an Intoxilyzer

8000C, traceable to an SI unit? I need a scientific answer.

A. So when the instrument is set up, right -- so

we talked about this, again, on one of the previous days,

that you're looking at the response that the instrument

produces in relation to a specific concentration of a

standard. And we know that a standard -- or alcohol when

it's present in the sample chamber will decrease the signal

that's produced. So you would expect that a standard of 50

will reduce the concentration -- will reduce the intensity of

light as it reaches the detector, different from the standard

at 100, which will have a greater decrease in the signal of

the intensity of reaching the detector, and even greater

again at 300. So you're looking at the response of those

standards relative to the standards that are produced. And

the calibration is then set and that is maintained by the

software, and any deviation in the calibration would be

picked up by the software, which would then trigger an

exception message. And the response of the subject test is

then applied to that calibration curve and it's relative

response is a decrease in the signal is relative to the

calibration curve and the standards that are used to generate

the actual number.

Q. And so there's a calibration curve that is

created. That calibration curve is created using - and this

is at the time of calibration at the factory - using the

reference standards. A calibration curve is created

electronically that relates the response of the instrument to

the indication?

A. Correct. Yes. And a check of that is done as

either a standalone calibration check or as part of a breath

test.

Q. And, and on the previous day I asked you

questions about how on earth it was possible to check the

configuration of a curve by using one data point.

A. I seem to recall that. I mean, that was about

a month ago.

Q. All right. So let's go back to the reference

standards themselves, because we have the Centre of Forensic

Sciences in the training aid saying that measurement relates

to SI units. We have the Canada Weights and Measures Act

that says that our measurements relate to SI units. That's

section 4(1) of the Weights and Measures Act, just for His

Honour's benefit. But both documents refer to something

called the General Conference on Weights and Measures. The

French name I won't try to pronounce, but its initials are

CGPM, right? And I'm going to pass up a bundle. My friend

received a copy of... no, that?

A. Okay, that's -- can I put this one away for

now?

Q. Yes, please.

THE COURT: You can put it up here if you want.

A. Are you sure?

THE COURT: Yes.

A. Okay. Sorry.

THE COURT: You're going to need a little more

room.

MR. BISS: Q. So from a scientist perspective,

whenever you are expressing a measurement in terms of an SI

unit, the definition for each element of -- each SI unit, and

I understand there are six or seven of them. The definitions

for each SI unit are defined by the International Brochure

for SI Units. So if you can just turn to -- Your Honour, I

put a tab on the copy I sent up to you so you can find it

faster. Page 95 describes what the International Bureau of

Weights and Measures is. It has its headquarters near Paris.

Now, these are the same people who keep the kilogram standard

and who define what a metre is, for example?

A. Yes.

Q. And their job is to establish fundamental

standards and scales for the measurement of the principal

physical quantities and maintain the international prototypes

for each of the units of the measure that we use around the

world, in particular in Canada, right?

A. I would assume so, if we are a member,

organization of that society.

Q. Well, in terms of membership in that society,

tab 7, the indication there is Canada became a member in

1907, and the representatives currently is Dr. James McLaren

from the NRC, in the International Bureau of -- Bureau

International Des Poids Et Mesures. So quantities and units

are defined in the SI brochure. That's tab 3 of this bundle,

right?

A. Yes.

Q. Okay. Now, at page 103, that's the second

tab, Your Honour, for your benefit. It says:

"The value of a quantity is generally expressed as

the product of a number and a unit."

[As read]

Now, what's the difference between a number and a

unit? Can you explain that from a scientific perspective?

A. Well, the unit is the reflection of what is

being measured and the number is the value that's actually

obtained.

Q. So a unit would be something like kilometres

per hour or....

A. Milligrams of alcohol in 100 millilitres of

blood, such as in this case.

Q. That's a unit?

A. Yes.

Q. And the number is the number that's associated

with it?

A. Correct.

Q. And in the second paragraph on that page, it

says:

"In order to establish a system of units, such as

the International System of Units, the SI, is it

necessary first to establish a system of

quantities, including a set of equations defining

the relations between those quantities."

Does that make sense?

A. Yes.

Q. So an SI unit is defined by the CGPM in the SI

Brochure, right?

A. You're using a lot of acronyms and a lot of

names.

Q. Okay.

A. I'm going to suggest to you that a lot of this

is probably beyond my scope of being able to deal with and to

be able to put it into any kind of context with respect to

breath testing.

Q. All right. But you would agree with me that

from a scientific perspective there is an International

System of Units?

A. Yes.

Q. When we were talking about milligrams per 100

mills, we are talking about milligrams as being a fraction of

a kilogram?

A. Correct.

Q. We are talking about mills as being a fraction

of a litre?

A. Yes.

Q. And a litre is defined as a cubic decimetre,

right?

A. I think we discussed that on the previous day,

yes.

Q. Right. So the question is, and the point is,

that all measurements in Canada need to be traceable to

reference standards, and the original reference standards are

established by an international organization called the CGPM?

A. I would assume so, yes.

Q. I mean, you don't know of any other place that

establishes the metre that we use in Canada, the kilogram

that we use in Canada?

A. You would have to talk to an organization that

is responsible for that. That's beyond my area of being able

to speak to it.

Q. But there is a concept in science called

traceability of a measurement result. Every measurement

result needs to be traceable back to the original SI units,

right?

A. Yes.

Q. So here is my question, a very, very general

question. How can it be the case that every subject test

stands on its own? Because if a subject test is a

measurement result, then surely it is a measurement result

that has to be expressed as a comparison back to the

reference standards, the SI units.

A. Well, in the case of a calibration, there

isn't a calibration standard for 130 milligrams of alcohol in

100 millimetres of blood. So when the calibration curve is

set up, it is extrapolated between the two points, between

100 and the 300, I think you said...

Q. Yes.

A. ...or between the 100 and the 50.

Q. In the creation of the calibration curve?

A. Correct.

Q. And that's why linearity of response is so

important.

A. Or nominal in the area in some cases.

Q. But ultimately what we are hoping to achieve

by designing or by setting up, by calibrating an instrument,

is to take something which is inherently nonlinear and turn

it into a linear response, so that if a given sample is

provided into the sample chamber of the instrument, that we

get an indication that comes out the other end that we can

rely upon, right?

A. Yes.

Q. And the way that we do that is by a

calibration of the instrument that takes place at a point in

time earlier than the date of the subject tests.

A. Correct. Yes.

Q. So every subject test does not stand on its

own. Every subject test is really a comparison with the

reference standards that were used when the instrument was

first calibrated.

A. I suppose you could look at it that way, yes.

Q. Well, that's the whole concept of traceability

in science. Every measurement result needs to be traceable

back to reference standards. That's, I would suggest to you,

a basic concept in science.

A. Yes. So in this case, this breath test is

traceable back to the standards that were use at the time of

calibration.

Q. And for His Honour's benefit, I would also

suggest it's a matter of Canadian law because of section 4(1)

of the Weights and Measures Act. So the point is, though,

sir, that measurements need to be traceable. Now, back a

long, long time ago, I sent off to you, and I think I sent

copies to my friend and to the police, a copy of a document

from NIST. What is, what is NIST? It's a U.S. entity?

A. That's correct. It's an organization that's

responsible for... I think I have that document.

THE COURT: Which document?

A. Sorry?

MR. BISS: The supplementary materials for

(indiscernible).

A. Okay. Oh, there we go.

Q. So what is, what is NIST?

A. It's an organization in the United States

that's responsibility for traceability of standards.

Q. And NIST has answers in their supplementary

materials of what methodological traceability is, right?

A. Yes.

Q. All right. So how do -- what answer do they

give with respect to what traceability is?

A. Well, that's defined in the first paragraph

there.

Q. Yes. And it suggests that it's the property

of a measurement result whereby the result can be related to

a reference through a documented unbroken chain of

calibration, each contributing to the measurement

uncertainty. Do you agree with that definition?

A. Yes.

Q. So traceability is not something that we think

of in terms of an instrument. It's not something we think of

in terms of a standard. Traceability is something we think

of in terms of a measurement result that is traceable.

A. Yes.

Q. And that's contained in the second section

there under (i)(a)(2). Only measurement results are

traceable.

A. Yes.

Q. (I)(a)(3), it's not organizations that are

traceable, it's a measurement result that is traceable?

A. Correct.

Q. Right? So once again, I want to suggest to

you that there's a problem with your approach in saying that

every test stands on its own. My respectful submission is

that every test has to be connected through an unbroken chain

of comparisons, traceable back to the realizations of the SI

units, right?

A. That is correct. However, each test is what

it is at the time of that particular test. And, again,

another test in time has no impact on that particular test

with respect to --

Q. That isn't what I asked you. I'm not asking

you about causation. I'm asking you about the traceability

of the measurement in science. I want to suggest to you that

if you don't know that the measurement result is traceable,

having a policy that says that every test stands on its own

doesn't tell us whether the measurement result is reliable or

not if you don't know anything about its traceability.

A. We know that the instrument is traceable back

to the standards that were used at the time of calibration.

Proper working order of the instrument is determined at the

time of the test.

Q. Yes.

A. And the response of that instrument to a

standard is evaluated at that time.

Q. Yes.

A. And the subject test is compared to the

original standards that were used at the time of calibration.

In this case we know that there was a standard that was

run...

Q. Yes.

A. ...shortly prior to this case -- or, sorry,

just prior to the breath test.

Q. Yes.

A. And a response was obtained and a numerical

value was obtained, so there was a decrease in the signal,

right?

Q. That's...

A. So then you have a subject test that's

provided that produced a signal that decreased the

sensitivity of the -- decreased the intensity of the light

that reached the detector, so we know that that result is

higher than that standard that was measured at that

particular time.

Q. All right. But my point is, that in assessing

the traceability of a measurement, one has to make reference

to the calibration. You've been talking about the

calibration by the factory and you've been talking about the

reference standards that were used at the factory, right?

A. Correct.

Q. So in determining the traceability of the

measurement result, one has to look back to does the

instrument have a calibration certificate and are there

reference standards that were used at the time of the

calibration certificate. And, fortunately with the

instrument that's before the Court, we have that.

A. Sorry, did you say "unfortunate"?

Q. I said "fortunately".

A. Oh, sorry, okay.

Q. Fortunately we have that. We know that

there's a calibration certificate from the instrument from

2009 that's been made an exhibit in this matter, and we know

that they used NIST reference standard 1828, which we know is

a reference standard, and you looked at the documentation of

NIST standard 1828 on one of the previous days. But the

point is, that that relationship, that traceability

relationship is relevant to an assessment of the reliability

of the results of the measurement results on the day of the

subject tests, right?

A. The result that's obtained is a comparison to

those standards.

Q. All right.

MR. BISS: Your Honour, could the bundle be made

an exhibit, please, and the NIST document?

THE COURT: Yes. What number are we at?

THE REGISTRAR: Forty-seven.

THE COURT: Okay. So 47 is the International

Measurement Standard binder, and then the NIST

traceability document, N-I-S-T, traceability

document be the next exhibit.

Reference: NIST Policy on Traceability (see also their Supplementary Materials follow link to Table of Contents on Traceability Questions and answers)

Reference: To build International Measurement Standards binder see bipm.org and download the following:

International Measurement Science Materials from Conférence Générale des Poids et Mesures, (CGPM) and its Bureau International des Poids et Mesures (BIPM)

Tab 1 The Metre Convention

Tab 2 BIPM Member States

Tab 3 SI Brochure

Tab 4 SI Summary

Tab 5 BIPM Governance

#traceability #policy #crossex

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Intoxilyzer®  is a registered trademark of CMI, Inc. The Intoxilyzer® 5000C is an "approved instrument" in Canada.
Breathalyzer® is a registered trademark of Draeger Safety, Inc., Breathalyzer Division. The owner of the trademark is Robert F. Borkenstein and Draeger Safety, Inc. has leased the exclusive rights of use from him. The Breathalyzer® 900 and Breathalyzer® 900A were "approved instruments" in Canada.
DrugTest® 5000 is also a registered trademark of Draeger Safety, Inc.. DrugTest® 5000 is "approved drug screening equipment" in Canada.
Alcotest® is a registered trademark of Draeger Safety, Inc. The Alcotest® 7410 GLC and 6810 are each an "approved screening device" in Canada.
Datamaster®  is a registered trademark of National Patent Analytical Systems, Inc.  The BAC Datamaster® C  is an "approved instrument" in Canada.