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Simulator is necessary "Accessory Equipment" that requires inspection and re-calibration

Updated: Sep 27, 2022

A wet-bath simulator is "accessory equipment" according to the ATC Best Practices document. A wet-bath simulator requires annual inspection to ensure that it will "continue to meet the manufacturer’s specifications".

In Ontario, Quebec, and other wet-bath provinces, the reliability of the simulator is essential to reliability of the "known" target value referred to in Criminal Code section 320.31(a). A liquid alcohol standard in a jar (the simulator jar) will not have a "known" target value unless the temperature of that liquid is carefully maintained close to 34.0 degrees Celsius. The temperature maintenance equipment in the wet-bath simulator (the metal housing on top and the probes) needs periodic inspection to establish whether or not it is performing in accordance with manufacturer's specifications.

Simulators that use digital thermometers, like the Guth 2100, require periodic inspection to ensure that the digital thermometer is performing in accordance with the manufacturer's specifications.

Simulator / approved instrument combinations where police use the RS 232 interface in the Guth 2100 simulator, rely upon that interface to provide information to the police officer and to the approved instrument as to the temperature of the wet-bath alcohol standard in the simulator. That RS 232 interface needs periodic inspection to ensure that it is working in accordance with the manufacturer's specifications.

Read the "Canadian Society of Forensic Science Alcohol Test Committee Recommended Best Practices for a Breath Alcohol Testing Program Effective: 2018 December 18":

It is important to realize that the issue for the Courts is not whether the simulator has been "inspected" within the last year. Whether or not the simulator has been sent out for maintenance 364 days ago or 370 days ago is not the point. The issue for the Court is whether or not the alcohol standard in the wet-bath environment is reliable at time of use. The results on the approved instrument cannot be used to make that determination because it is the alcohol standard that is supposed to be the "known", the approved instrument is not the "known" under 320.31(1)(a).

Defence lawyers will need to call an expert in "good laboratory practice" or in "metrology" to give expert evidence as to why the alcohol standard in the non-periodic-inspected wet-bath simulator is not reliable if they are to raise a reasonable doubt under 320.31(1)(a).

The keys to reliability of the alcohol standard in the wet-bath simulator will include the operator component, the calibration of the various systems in the wet-bath simulator to manufacturer's specifications, and the traceability of the alcohol standard itself. "Calibration" implies a time period within which the calibration of the wet-bath simulator is valid and outside of which the calibration is no longer reliable. A defence lawyer may wish to call a metrologist as an expert witness in this regard to raise a reasonable doubt under 320.31(1)(a) and explain the significance of "periodic" inspection and re-calibration. Below please find an excerpt from a paper presented at :

2007 NCSL International Workshop and Symposium Mark Kuster, Pantex Metrology

"Whether or not it is explicitly recognized and controlled by the calibration laboratory or customer, every calibration is associated with a time period during which the calibration is considered valid and after which it is not. More precisely, the calibrated instrument’s measurement uncertainty increases with time after calibration in a process known as uncertainty growth, and its measurement reliability, or probability that it will be in found in tolerance when recalibrated, decreases correspondingly. After a certain time period (calibration interval), the increased uncertainty and degraded measurement reliability drive the risk of measurement decision error beyond acceptable levels."


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