I agree that single point control tests and the Internal Test Procedure (ITP) check are good practice for police. The instrument shutting down, if the instrument detects an anomoly during a control test, or an ITP, is good design. However, these safeguards alone are not enough to ensure a scientifically reliable measurement result FOR A FORENSIC PURPOSE.
It is imperative that lawyers learn the differences between calibration of a measuring device at the factory or authorized service centre and control tests at time of use. The latter are very helpful in screening out bad tests, only if the device has been properly maintained, and the control test is done properly, using a reliable alcohol standard.
The problem is that although a single point control test, out in the field, should be good enough for a police officer yes or no decision, such limited evidence of reliability is not adequate for the forensic assessment of scientific reliability of a quantitative analysis. Scientific reliability of a quantitative analysis measurement result is a concept central to both the Motherisk Inquiry Report and the decision of the SCC in St-Onge Lamoureux. Scientific reliability of a quantitative analysis is established through, recent calibration as in Jackson, or recent re-calibration as in Vallentgoed, combined with strict adherence to standard operating procedures i.e. good laboratory practice.
Our job as defence counsel is to convince Canadian criminal courts, that Charter sections 7, 8, and 11(d) require that the Criminal Code of Canada, and other criminal statutes, that define delicts in terms of quantities and units, be construed and applied in accordance with good measurement science.