Causation of Error v. Calculation of Drift in Precision - Evidence Based Assessment of Reliability
Updated: Oct 10, 2022
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.
A good place to start in understanding reliability is ISO 17025. Buy a copy from ISO or ask your expert. The references in the cross-examination below are to the 2005 version. There is now a 2017 version.
A. I disagree with that opinion, and I’ve said my – I’ve offered my opinion before, that what happened at the time of those low calibration checks is of no use in determining the proper working order of this instrument at this time, and there’s no way to take that information and use it to collect and do statistical analysis on it, or take any scientific method and say what the effect of that was on the tests in question. It’s just – simply can’t be done because it doesn’t exist. The science doesn’t exist, the statistics, mathematical formulas, that doesn’t exist to be able to take information from another time and apply it to the tests in question and or what the magnitude of that impact would be. Q. All right. A. So, it’s a – it’s a great exercise as far as, you know, that, but it’s not useful or helpful at all, for determining the proper working order of the instrument in this case. Q. Well, my point though, is not whether or not data from a month before caused what happened a month after. That’s not the point. The point is that if we are trying to assess the reliability of an instrument at a point in time, we have to do a calculation of its accuracy and its precision and I’m suggesting to you that a methodology for looking at its accuracy and precision is the same methodology that you use at the Centre of Forensic Sciences with respect to blood, urine and alcohol analysis using gas chromatography. So, my question for you.... A. Okay, thank you. Q. I mean, if you were – if you were doing a gas chromatography measurement at the Centre and something
went wrong and there was a control check that didn’t look right, surely you would make a note about it. You would document it. You’d stop, you’d document it, and if you had to troubleshoot you’d – you would document that troubleshooting and probably you’d report it to somebody else. You would do all of those things, and that’s important so that other scientists, especially if they’re going to be making use of the precision calculation later on, with respect to other control checks associated with that instrument, that they know whether they can use those control checks or not, for purposes of calculating precision on the gas chromatograph. Right? A. When – in the laboratory when results fail because there’s a control outside, they’re not usually out by very much and the tolerance that we have is very small for accepting whether or not the results are not used or not – or whether they are considered qualitative as opposed to quantitative. And again, this is – the requirements for a forensic laboratory are different for that, that are used for breath testing. Q. Okay. But the point is, that in all of the international literature there’s a concept that you stop, you document, and you report. That’s an essential aspect of good laboratory practice, right? A. Correct. So, if my – one of my standards had failed, I would write on all of the results that were affected, I would be writing on that, that the control failed and that’s why the result is qualitative. And then I would repeat the analysis again. That result would be then reported as qualitative or repeated and of course, the next person who comes along, right, so that information is then entered into a database. Q. Yes.
A. Right? And then that information – so there’s a reason why the control failed. It’s outside the acceptable range. Q. Yes. A. It’s not like it was zero, right, which means I didn’t pipet anything into it at all, it’s just going to be just slightly outside. You would use that information to – calculating the measurement uncertainty over 365 days. Q. Yeah. A. So – I lost where I was going to go with this. Q. All right. I’m going to ask you a question. A. Okay. Q. I-S-O-17-0-2-5, you’ve heard of that document? A. I have, yes. Q. All right, and I’m putting a copy in front of you. And if you just confirm if that looks to you like IS- O-17-0-2-5, the version from 2005? A. Second edition, yes. Q. Page 1. Scope. Under paragraph 1.2 it says that, “This international standard is applicable to all organisations performing tests and or calibrations.” A. Yes. That’s what it says. Q. Do police services perform tests related to measurement? A. They do, yes. Q. Third paragraph, “This international standard is applicable to all laboratories, regardless of the number of personnel or the extent of the scope of testing and or calibration activities.” A. Correct. Last time I checked, police
services weren’t laboratories. Q. So why is it important from a forensic science perspective, that laboratories follow these kinds of practices when they’re doing measurement for forensic purposes, but not important for police when they’re doing forensic measurement? A. So, this is with respect to laboratories that oversee analyses. And in many cases in the United States, the laboratory is associated with the police service and they would actually do that. But here in Canada, we practice forensic science, especially breath testing, in a completely different way than they do in the United States. Q. So, police don’t practice forensic science. A. Oh, they do, as far as breath testing goes, in the United States when it’s associated with a laboratory. But here in Canada the police – and here in Ontario, specifically, the police service is in control of the program, not the Centre of Forensic Sciences. Again, we make recommendations about the things that they should do, about the kind of information and documentation that they should do, as well as quality assurance practices of what documents to keep, what to put in that – you know, when it’s required, documents with respect to testing and documents that are produced as part of testing to keep that. We make those recommendations but we don’t tell them what to actually do and they – we don’t have any sort of enforcing capability. Q. You have – you have no control over what police do in the case of non-conforming testing or calibration. C-F-S has no control over that, whatsoever? A. Correct. Q. The only entity that can possibly control the police in that regard, would be the courts.
A. I’m not sure the courts could even mandate that. Q. Well, if police services don’t follow rules with respect to good forensic science, is there any entity that you know of that is providing metrological supervision, and you understand what I mean by that? A. Yes. Q. That is providing metrological supervision of police measurement practices? A. Not that I’m aware of. Q. And yet, we face this situation in Canada where evidentiary breath testing needs to be done in a scientifically reliable way. A. It is. Q. So, the question is if there is no mechanism of enforcement, if there are no rules that are rules as opposed to recommendations, then how can there ever be any expectation of scientific reliability about what the police do? A. Because the program that’s currently in place will determine that. If there’s a result that’s obtained in a case that’s questionable that can be dealt with on a case by case basis. And so, I – as one of the three criminal coordinators in the Centre of Forensic Sciences lab along with Rachel Wallage and another colleague, we review all the cases which are submitted with letters of opinion, evaluating Intoxilyzer test record cards. Right? For either doing a back extrapolation or for providing an opinion on impairment or for determining the proper working order of the instrument. And so, perhaps once a month, right, we only see probably about 2,000 of these a year. There may be more cases than that, that we don’t see, simply because they’re within
the two hours. But when we do see cases where there’s an anomaly or something unusual, we will often contact the officers in charge and or the Crown attorney who may have submitted that letter of opinion, and say – oh, sorry – that there’s an issue with the breath tests that were done in this case and to withdraw the charges, withdraw the breath tests and or negotiate what they can, right. That’s totally up to them. But we do that on a regular basis. Again, there’s test record cards that we don’t see, and sometimes it’s brought to our – our attention from defence counsel that we meet in the courtrooms – in the hallways of courthouses where they’re asking us off – off the record, to look at these documents and see whether or not there’s anything unusual and should the Crown withdraw the charges, or any other issues, right? So, there is a mechanism for that, when there’s unusual occurrences that happen that those are dealt with and removed from circulation, if you will.
[So we rely on the CFS and the Crown Attorney to remove cases of unreliable equipment or unreliable procedure from the Justice system. The Defence can never litigate unreliability? The system does not need to be transparent? Science is whatever law enforcement says it is.]
#historicaldata #annualmaintenance #reliability #accuracy #Hodgson