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Traceability of Measurement Results is Through the Certificate of Calibration

Updated: Jul 5, 2022

"Traceability" is an important concept in metrology - measurement science. Defence lawyers need to study metrology, find experts, and retain experts (metrologists) to help all of us in the Court system to understand, among other things, the measurement science concept of "traceability".

In the forensic science, of evidentiary breath testing, the measurement results obtained using an approved instrument, are NEVER traceable to the 100 solution used by the police officer for cal. checks. The police officer cal. checks are merely control tests in accordance with operational procedures. Compliance with operational procedure promotes reliability but does not guarantee reliability, particularly if the measurement results are not traceable.

Every measurement result in science, including forensic science, must be traceable to reference standards or étalons. "53 mg/100mls" indicated must mean approximately 53 mg/100mls. "132 mg/100mls" must mean approximately 132 mg/100mls. "320 mg/100 mls" must mean approximately 320 mg/100mls. Each measurement result must connect with what mg/100mls means in the real world of measurement science. The meaning of mg is tightly defined in international measurement science. The meaning of ml is tightly defined in measurement science.1.

Although the cal. check solution (used for one or more control tests) may connect with a target value and a Certificate of an Analyst, the traceability of the measurement result produced on the Intoxilyzer is not dependent on, and has nothing to do with the control test(s). There is no system or circuit in an Intoxilyzer that mathematically or electronically connects a subject test measurement result to the standard alcohol solution in the simulator. The instrument does not compare the breath in the sample chamber to the alcohol standard in the simulator. The approved instrument and the simulator are two separate instruments. The Intoxilyzer does not "read" the simulator value and somehow combine that value with the subject chamber values to come up with a measurement result.

An Intoxilyzer generates measurement results across a wide range of approximately 8 to 400 mg/100 mls. Intoxilyzers, to be reliable, require linearity across many different BACs. Quite apart from the lack of electonic connection between the simulator value and the subject's sample chamber value, a solution at 100 mg/100mls tells you nothing about the reliability of measuement results at values other than 100, between 8 to 400 mg/100mls. Linearity of an IR instrument, like the Intoxilyzer, depends very much upon its calibration AT THE FACTORY (at time of manufacture) or by the Canadian authorized service centre (on subsequent maintenance).

The following is a sample cross-examination of a Crown expert on "traceability". This cross-examination needs improvement.

The purpose of this cross-examination is to lay the groundwork for the argument that traceability of the measurement results to the SI units, is through the calibration of the individual instrument, to reference standards - the étalons - SI units.

If reliability, requires traceability, then the Certificate of Calibration and the documents that verify the identity of the reference standards, used during that calibration, are relevant to the reliability of the measurement result at time of use.

Such relevance should drive disclosure requests for these documents.

Q. Now in – let me just find it. In Exhibit 12, on page 7, we have an example of – and this is with respect to Intoxilyzer 80 dash 0-0-4-6-3-2. A. The Intoxilyzer that was used in this case.

Certificate of Calibration Exhibit
Excerpt from Exhibit 12 - R. v. H.

Q. Yes. We have a certificate of calibration dated – I think it’s September 1st, 2009. A. It appears to be, yes. Q. And it appears to be a certificate by the manufacturer saying that on that date, that the instrument was calibrated using calibration solutions that were traceable to NIST. A. Yes. Q. Standard material, 18-28. A. Yeah. That’s what it says. Q. All right. Okay. Now, NIST is a reliable organisation? A. Yes, it’s a standard for references.

Q. We should think of it maybe as being the equivalent of the National Research Council in Canada? A. Ah, no, it’s a standard reference organisation. So, they have the references for weights and measures and temperature.

NIST certificate
Excerpt from Exhibit 27 Certificate of Analysis Standard Reference Material 1828 publicly available from NIST

Q. Okay. Okay, I’m showing you a certificate of analysis by NIST for a standard reference material, 18-28. A. This is the first time I’ve seen one of these. Q. I’ll just give you a moment to take a look. A. All right. Q. All right, so I want to suggest to you sir, that in assessing whether or not an individual Intoxilyzer 8000 or 8000C, if its measurement results are reliable, that both the certificate of calibration by the manufacturer that’s contained in the previous exhibit we referred to, and the NIST statement of traceability, of authenticity, of the – of reference standard 18-28, both of those items are relevant to an assessment, as a scientist, of the reliability of this particular Intoxilyzer. A. Well, you’re relying on the certificate of the manufacturer who said that they followed the procedures as recommended by ASCLD/LAB and used NIST traceable standards that that is information

that you can use to determine that the instrument is properly calibrated. Q. Yes. A. This is additional information beyond that... Q. Yes. A. ...that you would need for that purpose if you wanted to go into that kind of detail. Q. Yes. But if we wanted to establish whether

a measurement result on this particular Intoxilyzer 8000 or 8000C in this case, if those measurement results are reliable, then the certificate of calibration by the manufacturer indicating that its calibration and calibration solutions used are traceable to NIST and then another document from NIST indicating the quality of the measurement standard that was used, both of those documents are relevant from a scientific perspective, to the reliability of the measurement result on this Intoxilyzer 8000C. A. In the same way that a stand alone calibration check or a calibration check that’s performed as part of a breath test, does the same thing. It’s checking the calibration of the instrument. Q. You’re saying that – you said this morning that what is done during a periodic inspection of an instrument, when you were answering my friend’s questions. A. All right. Q. And you said that when a police officer is running a calibration check, on an instrument, that those are not calibrations... A. Correct. Q. ...of the instrument. A. That’s correct. It’s a calibration check. Q. But the certificate of calibration by the manufacturer is a piece of information that a scientist can use. The Court might use it as evidence of the reliability of any measurement result coming from that quantitative analysis instrument. A. Correct. And the reliability of that measurement is determined at the time of testing. Q. Well, you see, that’s where I think – and I think that’s the essence of the difference in the perspective

between you and Mr. Kupferschmidt, in that my suggestion to you is, that all the international scientific literature about measurement talks about the traceability of a measurement result. And in this case, we’ve got evidence, we’ve got information about the traceability of the measurement result on this Intoxilyzer 8000C through its certificate of calibration and through the calibration using standards from NIST which themselves, are traceable back to the Bureau International des Poids et Mesures that that’s the source of the traceability of the measurement in the international scientific literature. A. Correct. Q. What you’re saying is that that’s not important, that rather, all that’s important is a stand-alone calibration check at 100 milligrams per 100 mils. Not done under lab conditions. A. That's correct. That’s my position. That’s my opinion, be that of the Centre of Forensic Sciences and also the Alcohol Test Committee, ‘cause the traceability, you’re right, it goes to that certificate that was produced. That certificate was produced using standards and operating procedures by that organisation. But again, the proper working order of the instrument is determined at that time using a single standard. Q. Well, I’m not so much asking you about proper working... THE COURT: Can I just intervene just for a moment, Mr. Biss, just to address the last exhibit. Exhibit 27 is the National Institute of Standards and Technology Certificate of Analysis. EXHIBIT NUMBER 27: National Institute of

Standards and Technology Certificate of Analysis – produced and marked.

  1. Historically, there was ONE standard of volume for ale and wine in England. See Magna Carta. That rule is part of the law of Canada. See Weights and Measures Act.

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