Breath Testing Error Messages: Part 4
Invalid samples
Counterpoint Volume 2: Issue 2 - Article 2 (January 2018)
An article for participants in the myCAMprogram
Jan Semenoff, BA, EMA
Forensic Criminalist
I wrote in the last article on DEFICIENT SAMPLES that it was perhaps one of the most important articles you need to know and understand if your practice deals with breath alcohol testing. Consider this a notification that this article falls under that same category. Invalid samples constitute one of the most frequently encountered error messages generated during routine breath alcohol testing, yet are the error conditions most frequently mis-managed by breath test operators, often with devastating consequences for your client. Seriously, this article and the one on Deficient Samples should be considered part of your core curriculum in breath alcohol testing.
Invalid Sample (Mouth Alcohol Detected / Residual Alcohol Present)
Having said that as an emphatic preamble, INVALID SAMPLES should, in theory, be the easiest error message for you to deal with in your daily practice. The INVALID SAMPLE *** error message is generated when the test subject’s breath sample is not within acceptable slope limits and may contain fresh mouth alcohol contamination. Breath test operators are taught that the sample must therefore be considered contaminated with elevated levels of ethanol. In essence, the Residual Alcohol Detection System is warning the operator that mouth alcohol contamination is present and advising the operator to take the appropriate corrective action.
With that in mind, when properly managed by the breathiest operator, you should only ever see an INVALID SAMPLE error printout, with indications in the police report that another deprivation and observation period was properly performed, along with any corrective actions prior to obtaining further breath samples. The times should work out to indicate another complete deprivation and observation period occurred, according to your local regulations (typically 15-20 minutes).
*** It is a convention in this article that an ALL CAPS phrase such as INVALID SAMPLE or DEFICIENT SAMPLE indicates a screen message displayed on a breath testing device.
With that in mind, when properly managed by the breathiest operator, you should only ever see an INVALID SAMPLE error printout, with indications in the police report that another deprivation and observation period was properly performed, along with any corrective actions prior to obtaining further breath samples. The times should work out to indicate another complete deprivation and observation period occurred, according to your local regulations (typically 15-20 minutes).
*** It is a convention in this article that an ALL CAPS phrase such as INVALID SAMPLE or DEFICIENT SAMPLE indicates a screen message displayed on a breath testing device.
What corrective actions should the operator take?
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Typically, police breath test operators are trained to perform an additional observation and deprivation period of at least 15-20 minutes to allow for the dissipation of fresh mouth alcohol. However, the observation and deprivation period will only be effective if some additional corrective actions are taken. First, the operator should determine the source of the mouth alcohol contamination. Did the test subject burp? Vomit? Regurgitate? Do they have chewing tobacco present (and its’ remnants of small contaminating particles)? Is there a medical condition such as GERD?
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What is a substandard act or practice?
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What do we see too often?
However, often the breath device printout shows the next sample was obtained within two or three minutes of the original INVALID SAMPLE. The operator simply ignored the error message, pushed the Start Test button again, and started over with another breath test without performing another complete deprivation and observation period. I am of the opinion that obtaining the next breath sample in this fashion constitutes a substandard act on the part of the operator and likely contributes to falsely elevated readings. Any breath test results obtained in the second sample are therefore the product of a substandard act (with the contamination itself forming a substandard condition) and constitutes operator error. The sample reading produced must itself be a substandard result. In general, substandard results are not forensically or scientifically reliable, and should be discarded. |
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What is the scientific rationale for this?
Remember, if it takes 12-15 minutes for the burp, or mouth alcohol contamination to naturally dissipate, then waiting LESS than 12-15 minutes accomplishes nothing. The contamination may still be present in an amount that registers a false-positive reading. Testing under these circumstances is still under sub-standard conditions. However, the contamination may have dissipated to an amount that is not detected by the Residual Alcohol Detection System, and may therefore go unnoticed and unreported. The problem therefore is that the contamination may still be present, just unidentified. |
A better description for INVALID SAMPLE:
The cryptic INVALID SAMPLE error message may have been superseded by the more descriptive MOUTH ALCOHOL DETECTED or RESIDUAL Alcohol Present error messages by many devices. Many older devices still report the error condition as an INVALID SAMPLE, however, not necessarily identified by the Residual Alcohol Detection System.
Residual Alcohol Detection Systems deserve a number of articles to understand the depth of issues they present. Suffice to say, for now, that it is extraordinarily difficult for manufacturers to create an algorithm that reliably identifies mouth alcohol contamination. These so called “slope-detectors” have a fairly high failure rate (unless you buy into some of the latest revisionist articles out there that tout these detectors as nearly infallible).
The cryptic INVALID SAMPLE error message may have been superseded by the more descriptive MOUTH ALCOHOL DETECTED or RESIDUAL Alcohol Present error messages by many devices. Many older devices still report the error condition as an INVALID SAMPLE, however, not necessarily identified by the Residual Alcohol Detection System.
Residual Alcohol Detection Systems deserve a number of articles to understand the depth of issues they present. Suffice to say, for now, that it is extraordinarily difficult for manufacturers to create an algorithm that reliably identifies mouth alcohol contamination. These so called “slope-detectors” have a fairly high failure rate (unless you buy into some of the latest revisionist articles out there that tout these detectors as nearly infallible).
Errors of this sort are dealt with by having a deprivation or observation period before taking any additional samples to help ensure that no contamination has occurred or remained. If an error of this type is generated, the deprivation or observation period MUST occur again before any attempt has been made to receive samples for analysis. It is a sub-standard act to wait a minute or two, and simply push the Start Test button again and continue on. Regardless of the cause, the only remedy is the normal dissipation of ethanol over time.
Take a look at the following articles:
Take a look at the following articles:
- "Best Practice in Breath Alcohol Testing, Part One - Environmental Conditions" (Counterpoint, Volume 2, Issue 1, Article 6)
- "Best Practice in Breath Alcohol Testing, Part Two - Operational Considerations" (Counterpoint Volume 2, Issue 2. Article 1)
The importance of the pre-breath test observation and deprivation period
The notion of conducting a pre-breath test observation and deprivation period has been well established in breath alcohol testing protocols (Dubowski, 1985, 1991, 1994, 2008; Gullberg, 2003; Jones, 1987). Most manufacturer's instrument manuals and state training manuals and procedures follow a minimum 15-minute deprivation and observation period. The purpose of this deprivation and observation period is to provide a verifiable absence of possible contaminants, gagging, regurgitation of stomach contents, vomitus, burping or consumption of any substances. Any of these sources of contamination may falsely elevate the reported BAC results, artificially raising a legal amount of alcohol well beyond the per se limit. Therefore, standard testing protocols mandate that the observation and deprivation period be closely and continuously observed.
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We often see in the police breath room videos a lack of “close and continuous” observations, or the officer engaged in conversations with other officers, on the phone, performing paperwork, setting up the breath testing device, or otherwise with their attentions elsewhere. This does not perform the observation adequately. You might observe the officer with his back to the test subject a great deal of the time that they are together. If the officer does not keep the test subject under close and continuous observation, or re-start the observation period after they burp, gag or otherwise contaminate their oral pathway, the standard testing protocol has been violated. Any results obtained are the product of a sub-standard act and condition, and are by definition sub-standard in their reliability.
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The effect of mouth alcohol contamination on a breath test
Any burping, gagging or partial regurgitation would introduce contamination into the oral pathway. This must be given time to dissipate. If the time for dissipation is denied, then the reading obtained will be elevated beyond the true blood alcohol concentration.
Additionally, there is the issue that (in most jurisdictions), if two samples are received, they are obtained only a few minutes apart. This is not enough time for the dissipation of alcohol from the mouth and oral mucosa, especially since it is possible that fresh alcohol was introduced. As such, a condition where mouth alcohol can bias the true BAC reading of the test subject can occur. Under these conditions, it is known that the so-called “slope detectors” can falsely interpret this mouth alcohol bias and over-report the true BAC reading (Hlastala, 2006 and Gullberg, 2000).
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I would argue that best practice in breath alcohol testing should include a minimum of 15 minutes between breath tests. In my experience, this is never done in jurisdictions in the United States, where 2-4 minutes seems to be the de facto standard. Canada, on the other hand, requires a minimum of 15 minutes between the taking of breath samples, and further requires that the test results are within 20 milligrams/dL (or 0.02 grams/dL) of one another. Two reliable samples, unaffected by mouth alcohol contamination, can still be produced 20 minutes apart. It is highly unlikely that, given a 15 minute time between breath samples, that mouth alcohol contamination will occur at the same concentration each time to produce results within .02 of one another. It is a superior safeguard for the reliability and suitability of samples.
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Slope detectors & the residual alcohol detection system
It has been my experience that the slope detectors can, and often are, fooled under a variety of circumstances, most notably, recent consumption or regurgitation of an amount of alcohol, similar to what would occur during GERD emanation, which has a tendency to deposit alcohol-laden air in the oral cavity.
I have routinely observed the slope detector fail to register mouth alcohol that is as much as 12-15 minutes old, often allowing the unit to register an abnormally high reading given a simple swish of alcohol. Published studies indicate failure of the residual alcohol detection system to identify mouth alcohol bias between 37% (Harding et al, 1992) and 48 % failure (Simpson et al, 2004). Gullberg (2000) also reports on the inadequacy of the mouth alcohol detection systems. Harding reported that some of these failures occurred after more than 15 minutes of deprivation.
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Residual Alcohol Detection Systems are addressed in greater detail in the following Counterpoint articles:
Slope Detectors, Part 1: Form, Function and Purpose Slope Detectors, Part 2: Operational Considerations They are complex enough, and relied upon enough under circumstances that strictly are not warranted, and deserve greater attention than what is paid here. |
Shifting paradigms - A critical consideration
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The manufacturers and state agencies have worked hard to change the language of messages issued by the devices. Obviously, they don’t want “error” to be part of the lexicon. So, we see that newer devices no longer have “errors”. Instead, they report their “status”, or perhaps issue “exception” messages. Whatever. At the root of the matter is a condition, potentially substandard, that is being reported by the device in hopes that the operator will take the appropriate corrective action. Did they?
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Now, however, an even more concerning trend is emerging. I have participated in trials on a number of occasions where the INVALID SAMPLE error message generated a refuse breath test charge. I have heard operators provide testimony that the accused had, in effect, not complied with the breath sample demand by their intentional actions to subvert the breath sample, including the following:
- "Sucking back" or inhaling during, or at the end, of the sample provision
- Exhaling out the side of their mouth
- Exhaling too lightly
- Stopping and starting their exhalation during the sample
- Exhaling too forcefully
- Puffing their cheeks while exhaling
- Moving the mouthpiece in their mouth while exhaling
- Not exhaling "cooperatively" (what ever that might mean or imply)
The claim is that the test subject performed one of these sub-standard sample attempts as a means of refusing to provide the breath sample, and as a result, the INVALID SAMPLE error message appeared.
My main concern is that this is an inappropriate application of the error message. In short, INVALID SAMPLE occurs when the Residual Alcohol Detection System picks up a negative slope or drop on readings. So, in an attempt to re-create this error message in the manors described above in court, I had a number of test subjects who had consumed a minor amount of alcohol try and re-create these "bad" attempts at sample provision. The number of attempts is provided next to each "bad test" type, as shown in the following chart:
With different test subjects, each providing about ten attempts to produce each of the INVALID SAMPLE error messages, in NO case was the INVALID SAMPLE error message ever generated. Out of 310 total attempts, the only prompt ever displayed by the Instruments (Intoxilyzer 5000EN and 8000) was PLEASE BLOW. In each and every case, the PLEASE BLOW prompt was displayed after each "bad" attempt. and the end result in every case was a DEFICIENT SAMPLE error message when the device eventually timed out.
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In short, I simply can't replicate the INVALID SAMPLE error message by attempting purposefully to subvert the test process. I've actually tried far in excess of 310 times, with other test subjects under alcohol consumption conditions in training programs.
I can, however, easily create the INVALID SAMPLE error message by having a bit of alcohol contamination in my mouth while providing a sample, or belching just prior to sample provision. I can only conclude that the refuse breath test component of the INVALID SAMPLE error message is without merit. |
Final thoughts:
What are the important take-aways from this article:
- The INVALID SAMPLE error message occurs only when the breath test device identifies a downward or negative slope in the BrAC reading during the provision of a breath sample.
- When an INVALID SAMPLE error message is generated, a new deprivation and observation of a minimum of 15 minutes must be conducted.
- Any subsequent sample attempt after and INVALID SAMPLE error message less than the required 15 minutes may generate a falsely-elevated reading not identified as such by the Residual Alcohol Detection System.
- The INVALID SAMPLE error message cannot be generated by an attempt on the part of the test subject to subvert the breath sampling process.
Send me your questions or comments:
Comments and questions will be posted here with their responses:
Comments and questions will be posted here with their responses:
For further study:
- Dubowski, K.M. “Absorption, Distribution and Elimination of Alcohol: Highway Safety Aspects”, 10 J. Stud. Alcohol Suppl., 1985.
- Dubowski, K.M., The Technology of Breath-Alcohol Analysis, U.S. Department of Health and Human Services, Prepared for The National Institute on Alcohol Abuse and Alcoholism, 1991.
- Dubowski, K.M., Quality Assurance in Breath-Alcohol Analysis, Journal of Analytical Toxicology, Vol. 18, Oct 1994.
- Dubowski, K.M., Acceptable Practices for Evidential Breath-Alcohol Testing, Center for Studies of Law in Action, Borkenstein Course Materials, Indiana University, May 2008.
- Hlastala, M., Lam, W., and Nesci, J., The Slope Detector Does Not Always Detect the Presence of Mouth Alcohol, For the Defense, March 2006.
- Gullberg, R.G., The Inadequacy of Instrumental “Mouth Alcohol” Detection Systems in Forensic Breath Alcohol Measurement, Northwest Association of Forensic Sciences, Oct., 2000.
- Gullberg, R. G., Breath Alcohol Measurement Variability Associated with Different Instrumentation and Protocols, Forensic Science International 131 (2003) 30-35.
- Jones, A. W., Concerning Accuracy and Precision of Breath-Alcohol Measurements, Clinical Chemistry, 33/10, 1701-1706 (1987).
- Sterling, Kari, The Rate of Dissipation of Mouth Alcohol in Alcohol Positive Subjects, The Journal of Forensic Science, 2011.
