Breath Testing in Arizona DUI Cases
Breath testing in Arizona DUI investigations is junk science. It is not precise, and can print out a result that is more than DOUBLE the actual amount of alcohol in a DUI suspect's system. The average person trusts the results from the machine out of ignorance, and a strong marketing campaign by law enforcement, prosecution and the machines' manufacturers.
In Arizona DUI cases, breath testing generally falls into two categories:
1. A preliminary breath test (or PBT);
2. An evidentiary breath test.
PRELIMINARY BREATH TESTING
The preliminary breath test (PBT) is a handheld model used in the field (as distinguished from the larger evidentiary breath test models such as the Intoxilyzers covered below). They typically have an LCD readout, and lack the ability print the result.
In Arizona, the PBT is generally not admissible into evidence in court. This means that the prosecutor and police can not use the results against a person accused of DUI in Arizona in trial. Furthermore, a suspect has an absolute ability to refuse to submit to this test and it can not legally be held against them.
Why is this test used then? The preliminary (sometimes referred to as the portable breath test) is a tool used by law enforcement to establish probable cause to arrest a person, and also to give the officer a ballpark estimate of what an evidentiary breath test or blood test might produce. If you pass all of the field "sobriety" tests (which we don't recommend you take) and blow above or close to the legal limit on the PBT, the officer will likely arrest you despite your good performance on the field tests. The officer can then rely on the results of this test to convince a Judge in your DUI or MVD hearing that your arrest was legal.
Another recent use for the PBT has been in impounding vehicles for extreme DUI. In jurisdictions such as Scottsdale which take almost exclusively blood tests, an officer can easily justify impounding your vehicle for 30 days if you blow a 0.150 or more on the PBT. On the other hand, if you politely refuse to take this test then there is usually not enough evidence to sustain a decision to impound.
What if I know I'm below the legal limit... should I blow into the PBT? No, you shouldn't. The reason is that these machines are inaccurate, and if you blow it could make the difference between you being arrested or not. On the other hand, the officer will probably arrest you if you refuse. Nevertheless, we think the better course of action is to politely refuse and let a blood test sort it out (see below discussion of the right to an independent test).
PBTs are good party entertainment, and they are very useful in determining if there is alcohol in a persons system. However, they are not good at predicting a specific alcohol level, and they are not designed to detect impairment.
The most common PBTs are the Intoxilyzer 300 and the Alco-Sensor.
EVIDENTIARY BREATH TESTING
There is only one manufacturer which makes a current generation line of breath testing machines that is approved for use in Arizona DUI cases. That manufacturer is CMI. This company makes the Intoxilyzer of breath testing machines. Most people refer to this type of machine as a "breathalyzer." This is technically incorrect, as breathalyzer, like Intoxilyzer, is a brand name. Breathalyzers are not used in Arizona DUI investigations.
CMI's newest machine in the Intoxilyzer line is the Intox 8000 (pictured to the right) and it is in use in various jurisdictions throughout Arizona. The older machines that are still in use are the Intox 5000 line (shown in the picture above), which contains several incarnations. If you were unfortunate enough to take an Intoxilyzer breath test in Arizona, you should have received a copy of the machine's printout (commonly referred to as a "strip chart").
How can I tell which machine was used in my case? It should be easy to identify which Intoxilyzer model was used in your case based on the picture. However, if you don't remember or if the machine was hidden from your view, you can look at the strip chart (if you weren't supplied with one, it will be in the police report). Each Intoxilyzer in Arizona has a unique serial number. The Intoxilyzer 8000s start with "80" and the 5000 start with "64," "66" or "68" depending on the model. An example is 80-0001032.
In the Strip chart you typically find your name and the officer's name (except in the older Series 64 Intox 5000 machines). Your date of birth and weight will also typically appear.
Sample Printout Date from an Arizona Intoxilyzer 8000
| Test | g/210L | Time |
|---|---|---|
| Air Blank | 0.000 | 03:12:07 |
| Diagnostic Test | Pass | 03:12:34 |
| Air Blank | 0.000 | 03:12:01 |
| 0.100 Cal Check | 0.102 | 03:13:23 |
| Air Blank | 0.000 | 03:13:55 |
| Subject Test | 0.142 | 03:14:25 |
| Air Blank | 0.000 | 03:15:07 |
| Five Minute Wait | ||
| Air Blank | 0.000 | 03:20:07 |
| Subject Test | 0.147 | 03:20:41 |
| Air Blank | 0.000 | 03:21:24 |
| 0.100 Cal Check | 0.103 | 03:21:41 |
| Air Blank | 0.000 | 03:22:01 |
| Diagnostic Test | Pass | 03:22:20 |
In the above example, the yellow highlighted numbers are the person's results. All other numbers are part of the machine's test and calibration sequence. The two subject tests must agree with each other within 0.020. If they do not, then the test will not be valid unless it contains two samples that do agree within that margin. It is not uncommon to see a strip chart with three subject samples in Arizona DUI cases.
In the example above, the "0.100 Cal Check" is the measurement of a known concentration of gaseous alcohol. It is a safeguard relied on by police and prosecutors to convince Arizona DUI juries that the machine is working properly. The problem with this logic is that the Cal Check sample is known and controlled, whereas the human sample is subject to many variables.
Build in 10% Margin of Error: Each Intoxilyzer used in Arizona DUI cases has a built in and acknowledged 10% margin of error. This means that any subject result can be as much as 10% higher or 10 % lower than the number printed on the strip chart without anything else even going wrong with the test. Arizona DUI prosecutors regularly use a bell-shaped curve argument to try to convince juries that it is less likely that the subject results were off by a wide margin. Prosecutors use, and experts agree with, the following breakdown of the statistical probability relative to the 10% margin of error:
68 % of readings |
expected to fall within plus or minus 3 1/3% |
|---|---|
95% of readings |
expected to fall within plus or minus 6 2/3% |
less than 1% of readings |
expected to be off by the full 10% margin |
So they argue that less than 1% of all tests would be at the maximum of 10% low under this particular range. They try to make juries believe that the 10% margin of error is the only margin that matters in Arizona DUI cases, but this is not true.
Breathing Pattern: If a person holds their breath prior to blowing into a DUI breath testing machine, it can cause as much as a 15% rise in the reported result. Presumably, the longer the breath is held the higher the result. Studies have documented the result as applying where subjects held their breath for 15 seconds. No scientific study has been conducted for breath held less than 15 seconds, but there is no reason to think that breath held, but exhaled prior to 15 seconds, will not affect the results of the test. There are many possible causes of an abnormal breathing pattern. In fact, the machine is designed to assume that the subject inhales and then immediately exhales into the breath tube. Often times this is not the reality. Many officers instruct arrestees to take a deep breath and then wait several seconds before placing the mouthpiece into their mouths and instructing them to blow. The 15% margin of error for breathing pattern, according to most DUI experts, operates independently of the 10% margin of error listed above, making a possible 25% false high just from these two factors alone.
Breath Temperature: The Intoxilyzer machines are programed to presume a baseline temperature of the breath exhaled into the machine. If the temperature is higher than the machine expects, the machines used in Arizona are incapable of adjusting. The problem is that most people do not have the temperature that the machines presume.
Partition Ratio: The Intoxilyzers used in Arizona DUI cases are programmed to presume that the subject has a 2100:1 partition ratio. This means that it assumes that for every 2100 parts of alcohol in the person's blood there should be a corresponding single part of alcohol in the person's breath. The machine purports to measure the amount of alcohol in the breath and then it multiplies to translate the result into an expected blood alcohol result. The problem with this is that not everybody has a partition ratio of 2100:1. A person with a greater partition ratio will have a false low result, and a person with a lower partition ratio will have a higher result. How much higher? For people who are fully absorbed (meaning they don't have unabsorbed alcohol in their stomach) most experts will allow for the result to be up to 20% high based on this factor alone. Add this to the other sources of error mentioned above, and you can see that the Intoxilyzer machines used in Arizona DUI investigations are problematic.
But it gets even worse. Suppose a person has unabsorbed alcohol in their system. In this scenario, most experts will allow for up to a 50% false high.
Can partition ratio be tested? Yes, but since it changes over time and from drinking event to drinking event, it is impossible to test it after the fact to find out what a person's ratio was when the blew into an Intoxilyzer during their Arizona DUI arrest. The only way to test partition ratio is to take a simultaneous blood and breath test and compare the two results. Some jurisdictions in Arizona have started doing this. Most however, choose to use only one method or the other. Even so, prosecutors in Jurisdictions throughout Arizona, including Phoenix and Tucson, argue that partition ratio is irrelevant because it still takes an accurate measurement of a person's breath alcohol level. The problem with this argument is that alcohol in a persons breath can not and does not impair their ability to drive, or to do anything else. It is alcohol in a person's brain that impairs them, and it gets to the brain through the blood, not breath. So realistically, if we want an alcohol level that can measure a person's impairment, we have to use a blood standard, and this is why the Intoxilyzer machines make the calculation.
What do all of these sources of error mean for the average person's DUI case? The answer to this question depends on the skill of your DUI Attorney, the understanding and communication skills of your expert witness, the judge's willingness to allow the variables into evidence, and, in trial, a jury's assessment of the variables. Of course the higher your result the lower to probability that a jury will believe that the confluence of all of the above factors combined to produce a 0.270 when your actual alcohol content should have been in the ballpart of 0.07.
Admissibility of Intoxilyzer Results in Arizona DUI Courts: There is a very low standard governing the admissibility of the breath test results. Arizona DUI prosecutors simply have to show that the machine had been checked off as working "properly and accurately" in controlled tests prior to and following your test. In fact, there are preprinted forms, containing the title "exhibit" for this purpose. Assuming that the prosecution has these records and the proper boxes have been checked, then the breath test results (and strip chart) are admissible a legal mechanism commonly called the statutory method. If the statutory method fails for whatever reason (usually that the machine failed to pass the "exhibits,") then, in Arizona DUI cases, the State may call a forensic scientist or criminalist to provide expert testimony. If the expert says that they trust the machine's results then the breath test still comes into evidence.
Role of Defense Experts in Arizona DUI Trials: If the State uses the statutory method to admit the Intoxilyzer results they do not have to call their own expert. The police officers who testify against DUI defendants are generally not experts in forensic alcohol science or in the inner workings of a breath testing machine. So if the Defense does not call an expert, the result of the breath test often goes unrefuted. We believe that in many breath test cases it is unconscionable for a defense attorney not to call an expert, and in many cases think that it is negligent to the point of incompetence. We are amazed to hear that there are still law firms who accept an unrefuted breath test at trial without calling on an expert (assuming the state does not put one on). If the State does call an expert, then our attorneys can often get enough information out of them to make a case for reasonable doubt regarding the machine. That is probably why the Prosecution often times does not provide this chance.
Enter the Defense expert. Many Arizona DUI prosecutors don't want juries to hear the whole truth about the Intoxilyzer, and a Defense expert is crucial in relaying this truth. Assuming that the Judge will allow it, a good defense expert will have the knowledge to guide the jury through the variability and shortcomings of the machine. This expert may also be able to provide testimony regarding field tests (see the section on Field Sobriety Testing in Arizona).
State's Expert: Once a Defense expert has revealed the problems with the Intoxilyzer machines, the State will often times call a rebuttal witness, a criminalist of their own. In our experience, this witness will often times just give their opinion that there is a very slim chance that the machine was so far off in the case at hand to make a difference. There have been many trials where the State's expert, called in rebuttal, actually has sealed and delivered our not-guilty verdict. Most State's experts are honest and therefore can't help but bolster the Defense case, which is based on science. However, there are some State's experts who are essentially biased and beholden to the point of ignoring science. They seem to believe it is their job to convince juries of a DUI defendant's guilt rather than testify to scientific fact. We have all heard stories about experts giving bogus testimony for the prosecution in criminal cases (dental imprint testimony and finger print testimony cooked up to convict people of rape and murder). It is naive to think that even though this happens in serious dealth penalty cases that it does not happen in Arizona DUI cases.
A more balanced prosecution approach is, in our opinion, for the prosecutor to put their expert on in their case in chief and let the cards fall where they may. Instead, for strategy reasons, many prosecutors wait until after the Defense expert testifies, and call their expert if they think the Jury is starting to side with science and the Defense expert. This gives the State the advantage of having the last word in the trial (from witnesses). It also gives them a chance to make it appear to a jury that they didn't want to waste their time, but were forced to rebut misleading Defense evidence. Of course this is not reality, but in the courtroom it is as much about perception, and about primacy and recency, than about fact, truth and integrity. Many prosecutors realize this. Many prosecutors are competitive individuals. So are their experts.
Maintainance Records: Beyond the basic "before and after check" exhibits, the technicians responsible for maintaining the Intoxilyzer machines in Arizona are supposed to make notes of all maintainance done on the machines. The Intoxilyzer 8000 database program currently has a bug or lacks the functionality to record every instance of maintainance and every error. A software patch is expected but at this point there is no information as to when. When preserved, the maintainance records can tell us a lot about a machine. We can learn when the machine was taken out of service and why. We also often discover that a machine was taken out of service for a problem, and then the problem was unable to be reproduced in the crime lab or at the CMI factory.
Radio Frequency Interference: All Intoxilyzer machines used in Arizona DUI cases are supposedly equipted with a radio frequency detector. The idea is that, because extraneous radio frequencies can interfere with the results of the test (rendering a false low or false high), it is necessary to detect them to avoid this problem. The problem is that the radio frequence interference (RFI) detectors don't work well enough to detect and prevent result-changing interference. Recently the Phoenix crime lab all but acknowledged that RFI is an issue that can have a negative impact on a subject's breath test in DUI cases. In fact, there are rumors that Phoenix is considering switching away from their fleet of Intoxilyzer 8000 machines (which were recently purchased at great expense), and adopting a blood test standard.
To what extent can RFI affect my test? The answer is that scientists don't know. The only people who can really explain or conduct tests on the Intoxilyzer machine are the law enforcement departments who own the machines (CMI will not not sell them to DUI Defense Attorneys or the experts they hire, although some have managed to obtain them on the black market), and CMI themselves.
Don't be fooled. Just because it is the only manufacturer approved for use in Arizona (for recent machines), does not mean that it is the best, or that it is even fit to render a precise breath test in all cases (or even a ballpark estimate of a person's alcohol content in many cases). Whether the choice to only approve the Intoxilyzer (versus the Datamaster or the Draeger) in Arizona was a political choice, or a business decision, one thing is clear; it was not based on this being the best machine on the market. Both of the other machines have the capacity to measure breath alcohol level using two different technologies, so that one result may be verified against another. Not the Intoxilyzer, which uses only Infrared technology.