Cross Examination Of The BA TECH 101: A Back To Basics Approach To Creating Reasonable Doubt

By Steve Hayne


Our firm has been studying the BAC DataMaster since its inception as the “Verifier” in 1984.  A few years ago, we even bought a used one from a Rhode Island Police Department.  Over the past eight years my partners and I have examined the thing half to death; scrutinizing every electrode and eprom, processor and potentiometer, treatises, documents and forensic studies.  At times, we seemed adrift in a murky sea of technical data and scientific gibberish, with no land in sight.

I, the dimmest of the three bulbs, often felt paralyzed by the sheer wealth of information. Still, this was a good and worthy task.  After all, in the past years some of the best and brightest defense lawyers have persuasively argued that knowledge is power; that the path to an acquittal in a DataMaster case is paved with eproms codes and repair records.  And they were certainly right – in the past years.

The problems is that while we were busily searching out reasons for doubt in the  stacks of records and databases, very little moss was growing on Breath Test Program Director Rod Gullberg’s rock.  He, Tony McElroy, and the rest of the prosecution team were just as busily doing their level best to eliminate the source of these irritating technical challenges.  Today, the reality is that the Washington breath test program, has become largely insulated from the “traditional” technical attacks.

Why? For two reasons: (1) the State Toxicologist (working hand-in-hand with prosecutors), has succeeded in systematically eliminating many records traditionally reline on by the defense, and (2) many of the “bugs” which plagued the machine in years past have been eliminated.  The net result is that in more and more cases there are fewer records.  And by all indications, the trend will continue.

Is all then lost?  Have they finally bullet-proofed the breath test?  Is it now impossible to win a DWI case when the test comes in?  The answer is an emphatic no!

However, we must accept reality.  Just like in the old days of the Breathalyzer, good cases are still goof and bad cases are still bad.  When there is bad driving, bad physicals, bad attitude and bad breath test; yes, you have a bas case.  But in those more typical cases where the prosecution’s evidence is not a wall-to-wall defense disaster, numerous reasons for doubting the breath test can still be found.  From my point of view, the question is: Where should the battle against the many headed-monster be fought?:  Knee deep in the scientific swamp or with sound footing on the high ground – using the rest of the case to raise reasonable doubt?  In fact, these cases can still be won, but for difference reasons. 

I believe reasons for doubt exist in most cases, but it does take determination and preparation (and considerable courage) to take the monster on.  In other words, it’s a matter of changing focus, not careers. I’ll discuss ways to cross examine the tech in the absence of repair records later.  But first let’s an abbreviated look at how much the machine works.


In a nutshell, the DataMaster works as follows:  After the cop types in the “demographic” data, the machine runs a room air (“blank”) test and a check of its calibration using quart filter (“internal standard”) [See Appendix B and C].  The defendant is then instructed to expel a long, steady breath sample into a baffled mouthpiece inserted into the “breath tube” (a new mouthpiece must be used for each sample).  The breath travels down the tube (heated to minimize condensation) to the “thermistor”.  This device measures the air flow to insure that the defendant is blowing hard enough and with sufficient volume to give a “good” sample (ie; alcohol saturated deep lung air).

The breath then travels through the “three-way valve” and into the “sample chamber “, where the alcohol content is actually measured.  The measurement takes the place by passing a beam of “infrared light” through the sample chamber to the “detector”.  The light must bounce off mirrors at 45 degree angles (two 180 degree turns – see Appendix B) in the sample chamber (necessary to lengthen the light path for greater resolution).

If alcohol is present in the breath sample, the detector will measure a loss of energy which is assumed to be caused by the presence of alcohol.  In fact the defendant’s breath sample is tested four times per second as he or she blows into the machine, to make sure alcohol content is rising (as the breath comes from deeper and deeper in the lungs).  The goal is to get the most alcohol saturated sample possible. Thus, the longer one blows the higher the result (the real reason for differences between your client’s two breath samples).

The process of measuring the breath once every four seconds is commonly known as the “slope detector”.  This is designed to make sure that a “valid” sample is being introduced, since if mouth alcohol is present, the “slope” would be reversed, ie; a higher concentration at the beginning rather than end of the breath.  Should the machine detect an “invalid” sample, the test is aborted and the officer must start all over with a new 15 minute observation period. No record of the “invalid” test is retained in the database and an evidence ticket will not be printed.

When the detector sees alcohol due to a decrease in the amount of light striking the detector, it uses an extremely complicated (and secret) mathematical formula to compute the defendant’s breath alcohol concentration in vapor. The test continues with another “blank” (room air) test and then a test of the “external standard” (simulator solution).

The simulator solution is a mixture of alcohol and water which approximates a  .10 concentration in vapor.  The mixture, kept in a jar attached to the back of the machine must remain heated to 34 degrees Celsius (plus or minus .2 degrees).  This causes the evaporation of alcohol at a predictable rate into the space in the jar above the solution (per Henry’s Law).  It is from this air space that the machine sucks a sample for testing between the defendant’s two samples and the result must be between 0.90 and .110 (inclusive).  It is this process (along with other factors) which the State Toxicologist claims “certifies” the machine’s accuracy on each defendant’s test.

Next is another room air/blank test, followed by the defendant’s second sample, which must be within plus or minus 10 percent of the average of both tests in order to be “valid” (per WAC 448-13-060) [See Appendix D].

The test sequence ends with a final .00 blank test and the “evidence ticket” is printed out and ultimately used against the defendant at trial [See Appendix C].

Now that we know all we need about how it works, let’s turn our attention to attacking the results.


For those ambitious diehards who loved chemistry in high school and can’t wait to match wits with the state’s expert, hyper technical challenges still exist.  For one thing, even dummies like me can use the occasional error code and repair record to point out potential problems.  But for purposes of this discussion, I want to assume we don’t have either; we’re just plain stuck with the test result and obvious means to attack it.  Let’s further assume that we’re going to try the case to a jury.  With that in mind, let’s consider a few simple (but critical) rules:

1. K.I.S.S.  (Keep it Simple, Stupid)

Anyone who has tried a DataMaster case will enthusiastically verify that the more technical, complicated or distant the desired point is, the tougher it its to make — and, due to the convolutions necessary to get to it, the less impact it will have.  Remember (and keep reminding yourself) the jury knows nothing about infrared spectroscopy, analytical chemistry or the vibrating carbon-hydrogen bonds of alcohol molecules.  They just want to know if the machine worked in your client’s case or if there is some reason to doubt it.

As you prepare your cross examination (and prepare you must) keep in mind that the more complicated your question, the harder is going to (1) get the “correct” answer from the tech and,  (2) keep the jury attention.  You should find some solace in the fact that most successful lawyers who fought the Breathalyzer years ago avoided complicated technical challenges in favor of a more common sense approach.  We learned early on to limit cross to a few fairy straight-forward points which were then argued in summation.  So remember, keep it simple.  For instance-Right approach: Ms. Technician, you’ve conceded that the breath tube must be heated in order to avoid condensation, but isn’t it true offices Jones had no means other than touch to determine its crucial temperature?

Wrong approach: Ms. Technician, would you please explain to the jury the difference in micron wave lengths between the detection capability of the DataMaster for differentiating alcohol from acetone and it’s significance vis a vis the interferant detector?



Know where you’re going, why you’re going there, how you’re going to get there, and, when you’ve arrived. One of the paramount dangers confronted in cross examining any expert witness is not planning how to get where you want to go.  You should always have a firm point in mind before you start. You must then figure out how to get there, i.e; ask yourself how to corral the witness with foundation questions so that the point cannot be escaped.  Finally, don’t get greedy. Making points with some of these witnesses is like pulling teeth!  When you’ve made it. Leave it alone.

 For example, let’s say you want to make the point that the machine’s current software does not keep a record of the number two and three “error codes” (sample chamber temperature too low of high).


Wrong approach: Ms. Technician, does it make any difference that the Machine doesn’t keep track of the sample chamber t temperature error codes in the database?

This type of genaralized question is very dangerous.  It invites the State’s expert to make a speech which destroys the value point you’re trying to make.  The much better way to analyze the problem is thus:

(1) Where do you want to go?

You want the technician to admit the machine doesn’t keep a record in the database when the sample chamber temperature is either too low or too high (errors codes two and three) because the software in this State’s machine is not programmed to record them.

(2) Why do you want to go there?

To show the jury (1) the State chose software which fails to keep track of vital

Information and (2) if the temperature in the sample chamber was in fact too high or too low near the time of your client’s test, we wouldn’t know it, thus implying it could have been operating improperly near the rime of your client’s test. 

(3) How to get the desired information?

We must corral the technician with a series of simple leading questions designed

to make the desired end inevitable:Q: Ms. Technician, isn’t it true this machine uses something called “error codes” to identify problems in its operation?

Q: And in fact, those error codes are numbers which show up on something called the “database”?

Q: You recognize what I’m showing you, marked for identification as defense exhibit one, as a typical database, don’t you”

Q: And isn’t it true that a database such as this is a permanent record of all the breath tests performed on a machine, right?

Q: And also contained in the database is a permanent record of the error codes we spoke of a moment ago, correct?

Q: For example, if one were to see an error code number six on the database, it would show that a “fatal systems error” occurred in this machine, right?

Q:  And a “fatal systems error” means there was critical failure in the computer software, doesn’t it?

Q: And isn’t it also true that the reason the machine uses this error code system is so that anyone interested; technician, prosecutors, defendant’s or even the jury, for instance, would know when was problem with the machine?

Q: And isn’t it also true that the various error codes are numbered one through nine by the manufacturer?

Q: For instance, number six signifies the “fatal systems error” we spoke of a few moments ago, right?

Q: Now, the error codes numbered two and three have to do with the temperature in the sample chamber, don’t they?

Q: Number two means the temperature was too low and number three means it was too high, right?

Q: Now, the sample chamber is where my client’s breath was actually measured, isn’t it?

Q: And the temperature of the sample chamber is critical to the correct operation of the machine, isn’t it?

Q: And it’s also true, that the machine used to test my client’s breath in this case, is incapable of keeping a record of when the temperature in the sample chamber was either too high or too low in the database, isn’t it?

Q: So, if in fact that temperature was too high or too low near the time of my client’s breath test, we would have no way of knowing it, would we?1

Now, are you “there”? Some would say yes, other no, since we haven’t established the effect of a high or low temperature on the machine’s “accuracy”

condition 2 . My own philosophy is to make the necessary point, check it off and move on; saving further cross for rebutting the technician’s claim on redirect that it doesn’t really matter (if it comes).  However, it depends in part on how honest and straight- forward the particular technician in your case is being. If he or she is evasive and argumentative, leave well enough alone.  The point is this: you can see from this relatively simple example how long and difficult it can be to make the point.


From the thousands of witness I’ve cross examined over the years, this has been the most important lesson I’ve learned.  It is especially good advice when dealing with experts, since the way in which the question is asked can make a world of difference in the response one gets.


 1Note the question asks “near the time of the client’s test” rather that at the time.  The State takes the position that the machine would shut down and abort the test if it happened during a test sequence.


2Low hurts, high helps.

For example, let’s assume you want to show the jury that the “interferant detector” doesn’t always work properly.  How do you get that concession from the technician?

The wrong approach:

Q: Ms. Technician, does the interferant detector on this machine always work properly?

The result: even if it doesn’t, you are sure to get an unfavorable answer and a killer

speech to go with it.

Q: Ms. Technician, in the course of your training, you’ve certainly been made aware of the fact that there are many compounds on the human breath alcohol, haven’t you?

Q: In the course of that training, you were made aware of the study which identified as many as 102 such compounds on healthy human subjects, weren’t you?3

Q: Now it’s true, is it not, that the manufacturer was concerned enough about this problem that it attempted to screen a subject’s breath to make sure the result given was actually a measurement of alcohol rather than something else?

Q: In doing so, the manufacturer built into the machine something known as the “interferant detector” didn’t it?

Q: And it is also true, that this component is designed to screen compounds on the breath which appear similar to alcohol to the machine’s detector, isn’t it?

Q: Certainly you would agree with the manufacturer, that this component is critical to the correct operation of the machine?

Q: Now, it’s true is it not that you are aware of repeated instances in which the interferant detector has malfunctioned in DataMasters?

Q: Well, in fact, you have either personally observed or have been appraised of instances in which the interferant detector registered an interferant on one of the two breath samples, but nor the other, haven’t you?

Q: and in fact, you would certainly aggress that if an interferant appears on one of the person’s samples, it should appear on the other, shouldn’t it?4

Q: So we can safely assume, on those occasions when that happened, that the interferant detector wasn’t working properly, can’t we?

Q: And in fact, if it’s not working properly, something other than alcohol could be added to the alcohol reading and printed on the evidence ticket as alcohol.

It is obvious in both examples above, that getting to “the point” can be a laborious

process, made even more difficult by an uncooperative technician.  That is why the rules

of keeping it simple, knowing where you’re going and when to stop, and use if leading

questions are so important.



 3  Krotoszynski, et al in the journal of Chromatographic Science, 15 244 (1977), a

well known study with which the technician should have some familiarity.

 4th If the tech wants to play games with you, he or she will argue this point by

claiming that the interferant may have been  present just enough to trip the detector on

one sample by just have examples of detections well over that minimum level (.0099)

which were detected on only one sample.  Such examples are fairly plentiful.

What follows is Ken Fornabai’s excellent “Cross Examination Checklist” which

he generously allowed me to reproduce. It contains the best outline for cross examination

I have seen and you would do well to incorporate parts of it in your own cross.

Remember however, don’t get greedy.  It is better to make one reasonable,

salient, persuasive point then a dozen obscure, confusing and complicated allegations

Remember as well, that in the final analysis, by far away the best thing any defendant in

a criminal case has going is the presumption of innocence and requirement of proof

beyond a reasonable doubt.


1. Establish your credentials with the jury by going through steps for analysis

of a typical breath sample.

2. Establish the process by which the machine” measures a breath sample or

tests a breath sample.”

3. Emphasize the particular parts of the machine which have been repaired according to your repair records.  Establish that these parts are “critical”.

4. Establish that their testimony is a major part of their job.

5. Establish that the witness wasn’t there on the night in question so has no basis whatsoever for determining the effects of alcohol on the defendant.

6. Ask if the witness has reviewed the database prior to testifying.

7. Ask if the witness has reviewed their repair records or data base prior to testifying in court.  Then go through each of the repair that is part of tour theme should be very limited and always leading.

8. For instance: ask the witness to identify the particular repair record for your machine.

9. Establish that the witness had to either go to the field and repair the machine and write up what was done or take the machine to the laboratory for further repairs.

 Do not introduce the database.  When you are asking the witness about reviewing the records of the machine prior to testifying, just establish that he did not review the

database. Admission of the database is not necessary to prove the point and will simply confuse the jury.

10. Establish that the technicians are learning new things about the machine everyday.  That is things that they assumed would not occur did in fact occur. (Referencing Mr. Predmore’s study and Sgt. Gullberg’s study).

11. Establish that in fact the company who made the machine (Verax Systems) never made a breath testing device prior to the Verifier.  (Remember the forerunner to the BAC Verifier Datamaster II was the BAC Verifier.  The difference between these machines were outlined in the case if State v. Ford, 110 Wn. 2d 827 (1988).

12. Establish that initially when the State of Washington contracted for these machinery they had concerns about the company’s ability to produce machines in a timely manner and quality control.

13. Establish that the evidence ticket does not tell us whether or not the office correctly reports the temperature of the simulator solution or the breath tube.

14. Establish that the thermometer on the simulator solution jar is rarely if ever checked for accuracy.

15. Establish that the simulator solution does not go through the thermistor. 5

16. Establish that the solution is carefully prepared by State Toxicologist employees and it is tested on a Gaschromatograph (a much more sophisticated device)

17. Have him admit that a Gaschromatograph is probably the most universally accepted device to accurately measure alcohol levels of a particular substance.

18. Establish that this particular machine serial no. _______ will measure the external standard differently with each test.  For example, your database will reveal that although a new solution may have been installed, chronological analysis of the simulator solution when breath tests are administered will show a rise and fall of the alcohol levels of the external standard which cannot be attributed to depletion by evaporation.

19. Establish that the various DataMasters in use in the State will give different readings on the same batch of simulator solution.

20. If you have a spread between the two breath readings obtained in your

case, establish that the manufacturer claims the machine has a capacity for accuracy up to .003 (this is found in the operator’s manual) yet the State of Washington tolerates an accuracy level of .01(plus or minus).

21. Ask the technician how two readings could be so different when taken within three minutes of each other.  (Caveat: follow the rules set out above!  The technician will not be able to attribute the disparity in the two readings to burn off or absorption of alcohol, he will most probably indicate that the disparity can be accounted for by the “integrity” of the breath sample, i.e., how long your client blew).

22. Thus, this machine will determine the guilt or innocence of a person by how that individual blows into the machine or the “longer you blow he higher you go.”

23. Establish that the higher the reading the greater the difference between the two readings is tolerated.  (Plus or minus 10% of the mean of the two readings).

24. Establish that the machine is capable of saving a breath sample for re-analysis, but that this option was omitted in the State’s specifications to the manufacturer (what price is the truth?!)

25. Establish that the machine does not measure blood alcohol but measures alcohol in human breath.

26. Establish that strictly speaking it is alcohol on the brain that causes intoxication and not alcohol on the breath.  That is, one can have alcohol in the breath and not be under the influence of it, but one cannot have alcohol on the brain without it having influence.

27. Establish that the machine does not measure a blood alcohol level directly but employs a “partition ratio” standard of 2100 to 1.  (That is, it assumes the concentration of alcohol in the breath is 12100th of that in the blood).

28. Establish that the range of partition rations as reported in scientific

literature is as much as 1700:1 to 5100:1.


    5 See discussion in section II above

29. Ask the technician if he knows what your client’s partition ratio is.

30. Ask the technician if its possible for a person’s partition ration to vary from time to time and during the course of a day.

31. Ask the technician if it is important for the breath tube to be heated.

32. Establish that the operator is not required to check whether the breath tube is heated (he or she need only touch the tube to determine if it’s “warm”).

33. The State Patrol has done some test to determine whether or not a cold breath will affect the integrity of a breath analysis.  These studies have indicated that it probably would not, although the studies are very limited in number.  Approximately 8 tests were done on a cold breath tube.  However, if the technician testified to that, establish that there is a heating coil in the breath tube that is manufactured into the machine and the manufacturer would not put it there unless it served some purpose.


While the above “checklist” offers a variety of ways to attack the results, remember-the statements made are a lot easier said than done.  Choose just couple of points and prepare your cross on those points with meticulous attention to detail and with an awareness that the tech will avoid telling you what you want to hear.  Remember the rules set out above; K.I.S.S, map out your cross and lead, lead, lead.


With preparation and a little courage, even the most hopeless case will take on the rosy hew of reasonable doubt.

 Good luck.  Steve Hayne, November 17, 1992.