#linearity

Maybe the Instrument Is No Longer Linear Enough to Be An "8000C"

May 22, 2018
5 min

Maybe the Instrument Is No Longer Linear Enough to Be An "8000C"

Purpose: To explore the analytical variability of the 8000C as determined by the Alcohol Test Committee during evaluation of the 8000C prior to type approval. To compare the analytical variability of the individual 8000C used in the subject tests for the client with the analytical variability of the type or class 8000C determined by the Alcohol Test Committee. To suggest that the instrument in the matter before the Court may no longer be a member of that class or type because

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BAC Analysis in a Lab Without Bracketing Controls is at Best Qualitative not Quantitative

Stephen Biss

Apr 27, 2018
4 min

BAC Analysis in a Lab Without Bracketing Controls is at Best Qualitative not Quantitative

We have a serious problems in the Canadian criminal justice system. One of them is the failure of Parliament and the Courts to recognize the differences between a qualitative measurement (a screening device result like a rapid home use COVID test kit or a roadside breath ASD, PBT, or ADSE tester result) and a quantitative measurement that results in criminal law sanctions. The Criminal Code and our case law, to some extent recognize the differences between an approved instrum

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Change at One Point but Not at Another Point that is Equivalent

Stephen Biss

Apr 13, 2018
5 min

Change at One Point but Not at Another Point that is Equivalent

This is a sample excerpt from a cross-examination of a Crown expert using data from periodic inspection of an approved instrument. The multiple-point control test data from an annual periodic inspection in Ontario or from a re-calibration as in Vallentgoed can be very useful to the defence in cross-examing a breath tech or a Crown expert to identify drift in accuracy and precision over time. Purpose: To suggest that there is empirical evidence in the matter before the Court o

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Police Fail to Correct a Linearity Problem on In-House Annual Inspection

Stephen Biss

Mar 29, 2018
6 min

Police Fail to Correct a Linearity Problem on In-House Annual Inspection

Let's suppose that you obtain disclosure or Freedom of Information documents respecting In-house Periodic Inspections by your local police service of their approved instruments. What can you do with that information? Purpose of this example cross-examination: To obtain an admission from the CFS scientist that the disclosed annual maintenance records indicate that the police failed to take any steps to correct control tests on inspection that indicated the instrument's respons

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Why Does the ATC Say Single Point Control Tests are Good Enough?

Stephen Biss

Mar 25, 2018
6 min

Why Does the ATC Say Single Point Control Tests are Good Enough?

Purpose: To explore the differences between a measurement instrument that has a linear relationship between the thing measured and the result v. a measuring instrument that has a calibration curve. To search for an admission that the calibration curve can shift up or down, left or right, or rotate around a point over time. To cross-examine the CFS expert on the lack of empirical study supporting the ATC/CFS hypothesis that a single point control test can always detect drift.

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Stephen Biss

Mar 23, 2018
3 min

Response Drifts Over Time

In an article relied upon by the SCC in St. Onge, Brian Hodgson stated: Defence lawyers need to educate themselves about the meanings of "drift" and "over time". What is it that actually "drifts"? What happens "over time". Are these concepts important to clarify during any cross-examination of a Crown expert? Can the reality of drift over time be satisfied by single point control tests? Is more required to maintain reliability over time? The ATC and CFS regularly opine that a

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Stephen Biss

Feb 15, 2018
6 min

What is measurement?

Purpose: Cross-examination of a CFS scientist on the VIM. To connect "measurement" in Canadian evidentiary breath testing to "measurement" in the international literature, specifically the International Vocabulary of Metrology (the VIM Exhibit 18), referred to in most international scientific literature on measurement To define any measurement in Canada, including a measurement for a forensic purpose as a comparison. To obtain admissions from the CFS scientist as to the appli

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Control Tests do not displace Formal Calibration Intervals

Stephen Biss

Jan 13, 2018
7 min

Control Tests do not displace Formal Calibration Intervals

Purpose: To separate conceptually control tests from calibration To obtain an admission that there are no "assessors" in the province of Ontario To obtain an admission that the historical maintenance records show a deterioration of performance - deterioration of linearity in this particular instrument The strategy of using control tests as indication of reliability depends upon completeness of records and transparency To obtain an admission that at the bottom of the valley in

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Linearity Studies are Done on New Instruments not Aging Instruments

Stephen Biss

Jan 12, 2018
2 min

Linearity Studies are Done on New Instruments not Aging Instruments

Purpose: To obtain admissions that the published studies dealing with the linearity of approved instruments assume a new instrument recently calibrated by the manufacturer. Sample cross-examination of CFS expert on the inadequacy of studies relied upon by government scientists to maintain that approved instruments have good linearity - the studies were all done on new instruments, recently calibrated at the factory, not on aging instruments out in the field: Q. Well, every s

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Instrumental Deviations from Beer-Lambert Law

Stephen Biss

Jan 11, 2018
10 min

Instrumental Deviations from Beer-Lambert Law

This blog entry explores the use of a university textbook during cross-examination of a CFS scientist on "Instrumental Deviations from Beer-Lambert Law". The purposes of this cross-examination included: To explore the reasons why measurement instruments in the field may deviate from the linearity alleged by the Beer-Lambert law. To introduce a university textbook dealing with inter alia: External Calibration Creating a Calibration Curve Limits to Beer's law No longer linear w

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Beer-Lambert Law as Stated in Training Aid is Over-Simplified and Inadequate

Stephen Biss

Jan 10, 2018
10 min

Beer-Lambert Law as Stated in Training Aid is Over-Simplified and Inadequate

This blog entry contains excerpts from the cross-examination of a CFS scientist during an over 80 trial. It was suggested to the scientist that light in the Intoxilyzer sample chamber is polychromatic, rather than monochromatic. The Beer-Lambert Law as described in the CFS Training Aid assumes that the infrared light in the sample chamber is monochromatic, i.e. that there is one constant co-efficient for ethyl alcohol. Because the infrared infrared light in the sample chambe

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