Part 6: How does a DWI (driving while intoxicated) investigation in Austin, Texas work? Basics of the Breath Test Part 3: The Intoxilyzer 5000
When you first glance at the Intoxlyzer 5000, it looks like a pretty intimidating machine. It first went into use in the state of Texas in 1988. The current version of the machine was delivered in the late 90s. The machine is widely used throughout the United States and is uses a modified version of infrared spectrometry, which I discussed in an earlier blog.
In a nutshell, the Intoxilyzer has a chamber inside the machine. In the chamber infrared light shines from side of the chamber to the other. You should assume that when the chamber does not contain ethyl alcohol, the type of alcohol that you drink, that 100% of the light is going from one end of the machine's chamber to the other end. If for some reason this is not occurring, the machine should not be operable. The machine should run an air blank through itself in order to clear any residual alcohol that is in the instrument. If it isn't residual alcohol then in all likelihood it is a bulb issue or a software issue.
[The more complicated version of Infrared Spectroscopy. With thanks to J. Gary Trichter and W. Troy McKinney. In infrared spectroscopy, the alcohol level of a sample is detected by measuring the absorption of infrared energy in a gas. An infrared light with an optical filter emits infrared light energy of the type that is known to be absorbed by ethyl alcohol. Applying the Lambert-Baer Law, a law of physics, the amount of light that was not absorbed by the breath sample containing alcohol is measured and the concentration of alcohol in the sample can then be computed. The figure can be converted into a blood alcohol figure using Henry's Law, a subject we will address more in depth in a later blog.]
The machine is designed to be idiot proof. I was certified to use the Intoxilyzer 5000 EN in September of 2000. And I can tell you from personal experience, it is pretty much idiot proof. Most of the machines are left on at all times. After a 15 minute observation period, which is designed to try to negate any effects of mouth alcohol, you hit the green START TEST switch. Once you push START TEST a test sequence begins. If for some reason, your head happens to be up your ass and you push the START TEST button twice the machine will read INVALID TEST.
An Intoxilyzer Test Record will be printed at the end of each test. In addition, all results should be stored in the machines memory. The instrument automatically assigns each test a unique number, which is printed on the Test Record and stored in the internal memory.
The breath tube, the hose you see on the left hand side of the machine above, is a heated, reinforced plastic tube. The reason it is heated is to prevent condensation of water vapor or ethyl vapor. All breath samples and the room air used in the air blank sequences are directed to the chamber through this tube. (This means the arrestee blows into it. The hose also draws in an air blank to make sure there is no additional alcohol in the machine before each subject blow.)
The reference sample inlet is located on the right side of the instrument. The reference sample return is located on the right rear of the instrument. These two ports are used to connect the reference sample device (otherwise known as a wet bath simulator) to the machine.
The RESET switch is located on the back panel of the machine. When this rocker switch is activated NOT READY will appear on the display. The instrument should then conduct a circuitry check and return to the scrolling mode. The circuitry check is to make sure all of the hardware and software are working properly. It should be noted that the machine does this on its own without anyone there to make sure that the software or hardware is working properly. We are all supposed to assume that since the machine says it is working, it is working.
The keyboard in the front of the machine is used for data entry. Most modern breath testing machines have a card swipe for your driver's license and enters a lot of the information automatically. The Intoxilyzer 5000 is a bit of a dinosaur in the world of breath testing, yet it still remains on the United States Department of Transportation Conforming Products List of Evidential Breath Measurement Devices. It should be noted that CMI the manufacturer of the Intoxilyzer is up to the Intoxilyzer 9000.
The machine makes three distinct sounds to indicate different information. This is in case you are so stupid that you can't figure out what you just did or what needs to be done.
1. A short tone sounds with the completion of each step/operation. This is like, "Hey, attaboy, you are smart enough to follow the machine prompts."
2. A continuous tone sounds while the subject is blowing in the hose with sufficient pressure. (The goal is to get at least 1.5 ml of the subject's breath.)
3. A low-high tone sounds intermittently for several seconds when an improper condition exists. This means the machine is as screwed up as a football bat.
Now, back to the wet bath simulator. The organizer supports the Intoxilyzer 5000 and the reference sample device (simulator).
The reference sample device, also known as the simulator and the wet bath simulator, provides an alcohol/water vapor sample, which serves to verify the accuracy and calibration of the machine. The simulator is designed to deliver a sample with a known concentration of ethyl alcohol into the machine. It should be noted that this is all very mechanical and does not involve the imperfection of humans. The operating temperature is 34 degrees C +/- 0.2 (33.8 to 34.2 degrees C), or approximately 93.2 degrees F. The operator of the machine may verify that the sample is at the correct temperature by observing the thermometer on the front of the machine.
The stirring paddle then rotates to maintain an even temperature throughout the solution. The operation of the stirring paddle indicates that power is getting to the reference sample machine.
The heat cycle indicator is on when the heating element is on. The light will cycle on and off with the proper temperature is being maintained.
The inlet tube and outlet tube channel air through the reference sample machine and to the Intoxilyzer 5000 for analysis.
STANDBY MODE (INTOXILYZER 5000-68 EN ONLY)
The Intoxilyzer 5000-68 EN is equipped with a standby mode that is similar to the power saved mode of some personal computers. If the instrument is on but has not been used for a period of time, it will go into the standby mode. The POWER switch will remain in the depressed position, a red LED light located just below the POWER switch will be illuminated, and the display will be blank. To bring the instrument out of STANDBY MODE, press the START TEST switch. The instrument will display WARM UP PERIOD and should be ready for use in about 5 to 6 minutes. The Intoxilyzer 5000-68 does not have a standby mode.
Press the green START TEST switch once. The instrument will automatically conduct a series of diagnostic checks called circuitry tests.
The machine then prompts you step by step with a series of questions I like to call "Enter It Stupid."
Take a look at the TEST COMPLETE category. It is pretty disheartening. When you blow into the Intoxilyzer, you have to blow twice to make sure there are no contaminates that messed up the test. Interestingly, so long as the breath samples agree within a 0.020 g/210 L, you have a valid test. This is particularly distressing when you are talking about low BrAC cases where the subject blows between a 0.080 and a 0.090. The 0.02 agreement means if the subject blew a 0.08 on the first blow and then blew a second time, and the result was 0.06 that would be considered a valid test. The converse is also true. A 0.080 can just as easily be a 0.10.
THE STATE OF SCIENCE: Former Chief Scientist for Australia Professor Penny Sackett explores how we deal with uncertainty in science.
"As scientists, we know our measurements are imperfect at some level, but that doesn’t stop us from pursuing science." She goes on to state,
"Science is the interplay of three basic steps conducted in a never-ending cycle:
1) observation and measurement of nature,
2) organisation and synthesis to form models of nature (whether built of wood or computer algorithms),
3) development of predictive theories, or principles, that explain how these models interact.
The process is cyclical because the predictions of theories are tested with new observations. The more tests the theory “passes”, the better the theory. But there is always uncertainty due to a limited number of measurements, incomplete models, or assumptions that may be inappropriate.
The scientific process works precisely because the cycle of science generates more measurements, modifies models, and tests assumptions. When a scientist publishes a result, it takes the form of a number with an “uncertainty”. The result is not the number alone, but the number and the range of relative certainty taken together."
The irony behind all of these quotes is that they all seem to indicate that measurement is precise within a set of limits, and thus, imprecise. The State's expert will often argue the precision of the Intoxilyzer 5000 machine and ignore one of the most basic tenants of science - science is imperfect. Everything in this human world is imperfect. That is what makes it beautiful.