The Importance of the Wait, Deprivation, or Observation Period
Counterpoint Volume 3: Issue 1 - Article 1 (June 2018)
An article for participants in the myCAMprogram
Jan Semenoff, BA, EMA
Forensic Criminalist
This shouldn’t even be a “thing”. As simple a procedure as plunking the test subject down in a chair and watching them for 15-20 minutes before breath testing shouldn’t even warrant an article. But, for some reason, it does. I’ve had numerous cases over the years that had inflated reported BrAC readings stemming from an improper deprivation and observation period. We touched on this issue to some extent when we discussed the Invalid Sample error message.
See the Counterpoint Volume Two article: Breath Testing Error Messages Part 4 – Invalid Samples (requires Volume Two access)
See the Counterpoint Volume Two article: Breath Testing Error Messages Part 4 – Invalid Samples (requires Volume Two access)
What is best practice when it comes to conducting a proper deprivation and observation period?
Purpose and definitions
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The purpose of the Wait, Observation or Deprivation period is to provide verifiable elimination from possible contaminants, regurgitation of stomach contents, vomitus, burping or consumption of unknown substances. Any of these sources of contamination may falsely elevate the reported BrAC results, artificially raising a reported amount of alcohol well beyond the per se limit. Therefore, best practice testing protocols dictate that the Wait, Observation or Deprivation period is closely and continuously observed. If the period is improperly conducted, then the results obtained, regardless of an .02 agreement, are inherently unreliable, and should be disregarded.
Let’s start by defining some terms that are often used interchangeably: |
Wait Period:
This is the most generic of terms to describe a 15-20 minute period of time before an evidential breath alcohol test. Recent consumption of alcohol is of great concern. You will see that trace amounts of alcohol can find their way into the testing cycle, and NOT be detected by the RADS (Residual Alcohol Detection System) algorithm. This leads to the necessity of the so-called “Wait Period”, a necessary delay of at least 15-20 minutes from last consumption of alcohol to ensure any residual mouth alcohol is properly dissipated. But notice that simply “waiting” doesn’t imply any measurable performance standard. We simply “waited” a period of time before taking the breath test. So what…?
This is the most generic of terms to describe a 15-20 minute period of time before an evidential breath alcohol test. Recent consumption of alcohol is of great concern. You will see that trace amounts of alcohol can find their way into the testing cycle, and NOT be detected by the RADS (Residual Alcohol Detection System) algorithm. This leads to the necessity of the so-called “Wait Period”, a necessary delay of at least 15-20 minutes from last consumption of alcohol to ensure any residual mouth alcohol is properly dissipated. But notice that simply “waiting” doesn’t imply any measurable performance standard. We simply “waited” a period of time before taking the breath test. So what…?
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Deprivation Period:
Prior to receiving samples of breath, the technician must ensure that the subject’s mouth is free of foreign materials such as breath mints or candies, gum, medicines and inhalers, breath fresheners or mouth washes, chewing tobacco, and any other possible source of interferents. Many of these substances do contain trace amounts of ethanol. Some, such as the chewing tobacco, are believed to trap alcohol (Some people choose to drink their alcoholic beverages with a wad of chewing tobacco in their mouths that absorbs the alcohol in the beverage). Yuck! |
Again, this Deprivation Period is much the same as a generic Wait Period, with an only slightly greater performance standard implied. The test operator has simply ensured that nothing was placed in the mouth prior to taking the evidentiary breath sample. This is better than a simple Wait Period, but not by much.
Observation Period:
An Observation Period, on the other hand, implies that some sort of defined action was performed – the test subject was, at the very least, “observed”. What were they observed for? Burping, regurgitation, and vomiting are potential sources of fresh mouth alcohol contamination. If these situations occur, the testing process must be delayed allowing time for any contaminating residual mouth alcohol to dissipate. Water will also lower the mouth temperature and dilute the test results, resulting in a lower BrAC being obtained.
In short, Non Par Orum, or Nothing by Mouth, should be the rule rather than the exception.
An Observation Period, on the other hand, implies that some sort of defined action was performed – the test subject was, at the very least, “observed”. What were they observed for? Burping, regurgitation, and vomiting are potential sources of fresh mouth alcohol contamination. If these situations occur, the testing process must be delayed allowing time for any contaminating residual mouth alcohol to dissipate. Water will also lower the mouth temperature and dilute the test results, resulting in a lower BrAC being obtained.
In short, Non Par Orum, or Nothing by Mouth, should be the rule rather than the exception.
Best practice:
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A Deprivation and Observation Period:
Combining these last two protocols is the best practice in breath alcohol testing. Depriving the test subject of the opportunity to place anything in their mouth, coupled with a period of close and continuous observation of the test subject lessens the possibility of false positive readings. Notice I said lessens the possibility. The contamination can still occur and go unnoticed by the RADS algorithm, which determines the suitability of the sample by identifying a “drop” or “negative slope” in the reading. |
Figure 1 - Contamination in red, compared to the true BrAC level shown in blue.
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Close & continuous observation
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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. Some state agencies require 20 minutes, and in this case, longer is better. 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.
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Therefore, standard testing protocols mandate that the Observation and Deprivation Period be closely and continuously observed. Merely being in the room, attending to paperwork or setting up the breath testing device without monitoring the test subject is insufficient. I frequently see breath room videos where the arresting officers are doing paperwork, chatting on their phones, or in conversation with other officers, often in and out of the breath test room. The breath test operators often are engaged in other activities and are not monitoring the test subject. Remember, it is not the gregarious burp noticed across the room that is the issue. It is the polite, unnoticed, undetected little burp (micro-burp?) that contaminates the oral pathway leading to an artificially inflated reading that is of concern. It is these undetected sources of contamination that need to be identified so that the observation and deprivation period can start again. This necessitates close and continuous observation of the test subject.
Of course, the effectiveness of the Observation and Deprivation Period is predicated on the assumption that it is carried out correctly. If either the arresting officer or testing technician do not perform this observation period adequately the results obtained, regardless of an .02 agreement, are not reliable, and should be disregarded.
Time required
In practice, the observation period should be at least 15 minutes long. The manufacturers’ training manuals for various instruments, and the US DOT BAT Instructor’s Curriculum Manual recommend a wait period of 15 minutes. Many jurisdictions seem to push toward a 20-minute wait period. You will see that the dissipation of fresh mouth alcohol occurs within 12-15 minutes in actual subjects. Again, the prudence of waiting 15-20 minutes increases the perceived reliability of the testing process.
When does the Wait Period Time Start?
There has been debate in court as to when the observation period should begin. Does an officer, driving to the police station, sitting in front of a subject, divided by the “silent patrolman” have a degree of observational ability? Must the observation period be re-started after the subject has had a telephone conversation in private with legal counsel? Must the observation period be performed by the qualified technician, or the arresting member? Debate continues.
There has been debate in court as to when the observation period should begin. Does an officer, driving to the police station, sitting in front of a subject, divided by the “silent patrolman” have a degree of observational ability? Must the observation period be re-started after the subject has had a telephone conversation in private with legal counsel? Must the observation period be performed by the qualified technician, or the arresting member? Debate continues.
Regardless of the debate, it boils down to a performance standard. If the officer’s Deprivation and Observation period are compromised (performed in a sub-standard manner), the potential for fresh mouth alcohol contamination to occur exists. If the Deprivation and Observation period are sub-standard, then the results obtained by the evidentiary breath test are also compromised or sub-standard. Sub-standard results cannot be considered scientifically reliable. Scientifically unreliable results cannot be relied upon “beyond a reasonable doubt”.
The suitability of two samples received
.02 Agreement
In most jurisdictions, two breath samples are received that have to correlate to one another before the lowest of the two values is reported as the measured BrAC. For some reason that has never been completely explained to me, the typical correlation is a value of 0.02 g/dL agreement. That means that the two samples must be within 0.02 g/dL of one another to be considered reliable. As an example, if the first test generated a result of .100 g/dL, then the acceptable range for the second test result is between .080 and .120 g/dL. This means that any readings between 0.080 and 0.100 g/dL are acceptable, or conversely any reading between 0.100 and 0.120 g/dL are within the acceptable range.
In most jurisdictions, two breath samples are received that have to correlate to one another before the lowest of the two values is reported as the measured BrAC. For some reason that has never been completely explained to me, the typical correlation is a value of 0.02 g/dL agreement. That means that the two samples must be within 0.02 g/dL of one another to be considered reliable. As an example, if the first test generated a result of .100 g/dL, then the acceptable range for the second test result is between .080 and .120 g/dL. This means that any readings between 0.080 and 0.100 g/dL are acceptable, or conversely any reading between 0.100 and 0.120 g/dL are within the acceptable range.
Figure 2 - The range of potential values that could be accepted as reliable after the first BrAC test result is obtained.
But, let’s follow a specific line of reasoning concerning the notion of .02 agreement… and why it is insufficient:
- In most US jurisdictions two samples are obtained about 2-5 minutes apart (assuming two samples – places like New York and Kansas still obtain only ONE sample – a forensically unsound practice).
- It has been well established that normal dissipation of fresh mouth alcohol takes a minimum of 12-15 minutes.
- Therefore, 2-5 minutes is insufficient to allow for normal dissipation to occur.
- Therefore, taking a second sample within 2-5 minutes of the first is unsound practice, as the normal dissipation cannot conceivably occur in this short time period.
- Therefore, best practice dictates that the second sample should be taken after 15 minutes, to allow for the normal dissipation of potential contaminates. Unfortunately this does not occur in the majority of locations.
By the way, this “more than 15-minutes between samples” breath test protocol is standard practice in Canada, and some other jurisdictions around the world. It is hard to argue in these areas that two burps occurred, 15 minutes apart, that contaminated both samples with an .02 g/dL agreement.
Conversely, under circumstances where a second sample is obtained within 3-5 minutes, the potential for mouth alcohol contamination to over-report the true BrAC and fall within the .02 agreement window IS possible. This makes a properly conducted Deprivation and Observationperiod all the more necessary.
Operator error
Under certain circumstances, the Invalid Sample error message may be generated. The circumstances are precisely what the Deprivation and Observation Period are designed to identify – burps, regurgitation, etc.… Unfortunately, the breath test operators occasionally do not identify the Invalid Sample error message as requiring a new Deprivation and Observation Period.
Errors of this sort are dealt with by having a Deprivation and Observation period before taking samples that helps to ensure that no contamination has occurred. 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.
What is NOT protected by a proper Deprivation & Observation Period?
It is important to know that ANY mouth alcohol contamination that does NOT produce the negative slope described in Figure 1 will NOT be identified by the RADS (Residual Alcohol Detection System) algorithm. If the test subject has leakage from the stomach from GERD, or any other medical conditions, waiting 15-20 minutes will make NO difference to the reported results. Contamination will still occur.
Figure 3 - Wait all you want, if the contamination is consistent, and caused by some sort of medical condition, the reported BrAC results will still be falsely elevated.
Best practice:
So, what is the best practice when it comes to wait, deprivation or observation periods?
- First, the operator conducting the evidentiary test should inspect the test subject's mouth. Any contaminates should be removed.
- The test subject should be allowed to rinse their mouth if contaminates could conceivably remain - i.e.: Chewing tobacco. This act starts the deprivation and observation time.
- Next, a period of no less than 15 minutes should elapse. Even better practice is to use a 20-minute time period. This period of time should commence in the breath test room just prior to receiving samples, and cannot be conducted in the patrol car, while at the booking desk, etc.
- The period of time should be considered both a deprivation and observation period.
- As a performance criteria for observation, the breath test operator should be in close and continuous contact with the test subject.
- If the period of close and continuous observation is broken, the deprivation and observation period should be re-started.
- If any error or status message is issued during any breath test sequence that indicates the presence of fresh mouth alcohol contamination, the deprivation and observation period should be re-done, and a new evidentiary breath test sequence conducted.
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Practice Tip:
Sounds simple? Pay attention to booking sheet times, arrest times, breath times, driving times, body cam time signatures, etc. Upon examination, the actual deprivation and observation period may be quite different than the times stated in the police report. |
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., “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.
