Causation of Error v. Calculation of Drift in Precision - Evidence Based Assessment of Reliability
What is the purpose in Stinchcombe/McNeil disclosure or O'Connor production of maintenance records and historical data?
Crown CFS scientists are right in saying that there is no causal relationship between the historical data and the results of a subsequent subject test.
Crown CFS scientists are incorrect in saying that maintenance records and historical data are irrelevant in assessing the scientific reliability of a measurement result.
Control tests, cal. checks, and simulator temperatures do not change Intoxilyzer results! They do not cause error in Intoxilyzer results! You can operate an Intoxilyzer and get an accurate result with no wet-bath simulator or dry gas attached to the Intoxilyzer (however you would get zero cal checks).
The point is scientific reliability of the measurement result. Lawyers need to understand the meaning of "scientific reliability of the measurement result"
Lawyers and Judges need to understand that many factors determine the correctness AND RELIABILITY of the tests.
The many factors are NOT limited to factors apparent at the time of the subject tests.
If a Crown, Judge, or CFS scientist starts heading in the direction of asking defence to prove malfunction or operator error causation of the results, a conscientious defence lawyer needs to re-direct the Court's direction to impact on "reliability" as contemplated by the SCC in St-Onge citing the Hodgson paper and R. v. Lam in Ontario.