Selecting and Using Defense Experts in the DUI Trial

by Patrick T. Barone, Barone Defense Firm, Birmingham, Michigan

The following is an excerpt from the upcoming 2010 supplement to Defending Drinking Drivers:

The Selection of the Defense Expert at Trial

The expert witness has become an important member of the defense team in many drunk driving cases. Per se statutes have enhanced the importance of chemical evidence and, therefore, have often necessitated the use of expert testimony to analyze, question and rebut the state’s chemical evidence. Properly used, expert witnesses can aid the attorneys, the judge and the jury in understanding many of the crucial issues surrounding the guilt or innocence of the drunk driving defendant.

However, an attorney should never use an expert as a substitute for his or her own lack of knowledge regarding the science of chemical testing or the metabolism of alcohol. Attempting to use an expert to “fill in the gaps” of one’s own knowledge is almost sure to meet with disaster at trial. Many of the references needed to gain this knowledge are listed in the bibliography of this treatise, and there are also many excellent advanced training seminars presented throughout the country each year.

Additionally, unless the expert can make the attorneys, the judge and the jury understand his or her testimony, the expert’s reception will be disappointing. The expert witness is in a precarious position because the presentation of his or her arguments depends upon the questions of the attorney. Therefore, the framing of the questions determines to a large extent the kind and effectiveness of the expert’s answers. This is another reason why the defense attorney must have a vivid understanding the legal and scientific issues involved in the client’s case. Armed with such an understanding, the defense attorney will know how to ask questions that will produce the most helpful answers. On the other hand, uninformed and uneducated questions from counsel usually result in a reinforcement of the State’s scientific evidence.

Careful preparation requires adequate consultation between you and your expert witness. Decisions on the order of the questions, the methods of attack on the chemical evidence, the emphasis to be given certain data, possible hypotheticals and final summary questions should be made carefully. You and your expert witness should (a) agree on the purpose of the evidence to be presented, (b) have examined the essential questions that may be raised by the state in cross-examination and (c) have reduced the total presentation to brief, clear and concise argument.

Defense counsel must first be satisfied that the expert has the requisite knowledge, skill and experience to testify at trial. Defense counsel must also make the appropriate arrangements with respect to the expert’s fee and be sure that the expert will be available for consultation and trial when needed.

With a little time and effort, finding an appropriately qualified expert should not be difficult. There are many expert witness directories available on the internet. There is however no substitute for word-of-mouth recommendations. Ask other lawyers who aggressively handle drunk driving cases which experts they’ve successfully used in the past.

If your proposed expert has no track record of which you are aware, then you should consider checking the expert’s references and to verify their CV so that the expert does not embellish, fabricate or enhance his or her credentials. If you don’t verify everything, then you can bet that the prosecutor almost certainly will. Thus, when the fraud is uncovered, the testimony that you worked so diligently to perfect may cause nothing but embarrassment for you and your client. A sure-fire way path to the one-word verdict is by way of judge or jury’s opinion that your expert is not a truth-teller.

Preparing the Defense Expert for Trial

Once the expert’s credentials have been checked, and you are satisfied that the expert can help your case, the expert must be prepared for trial testimony. The following points should be considered and addressed when preparing to use an expert witness and in preparing his or her testimony at trial:

  • Well in advance of trial provide the expert with copies of police reports, witness statements, log books, maintenance records and any other information available to you that relates to the proposed area of testimony. It may also be desirable for the expert to interview the client. This will preclude a series of cross-examination questions related to the expert’s lack of personal knowledge about your client or about the facts of the case.
  • Research the law to confirm that the proposed area of testimony will be admissible and that your expert will meet the necessary standards and criteria set forth in the relevant court rules. It is your job to confirm that the expert will be qualified and in fact allowed to testify. An unsuccessful attempt to have your expert qualified is another sure-fire path to a one-word verdict.
  • It is also your job to educate the expert on such legal issues that may bear upon his or her testimony, and to simplify them wherever possible. Just as you are relying on the expert to help educate you on the science involved in your case, he is relying on you to educate him on the law involved. Doing so will help the expert cater her testimony to the specific laws in your jurisdiction.
  • Take the time to fully learn and understand the science that underlies the expert’s opinion(s). In doing so you should review any relevant scientific authorities including textbook chapters or science journal articles. After the factual and legal issues supporting your theory of the defense have been discussed and evaluated with the expert, and you are confident that you fully understand them, you must synthesize all of this knowledge with your theory of the case. You must also use this understanding to prepare your voir dire, opening statements, direct questioning, and closing argument
  • The expert’s opinions must be based upon science and not upon speculation. The expert’s opinions must also be consistent with the version of facts that you know will be presented to the trier of fact. There is no benefit to be gained in having your expert prepared to testify about a rising blood alcohol defense if the requisite facts needed to make out this defense will not be received in evidence.
  • Confirm that the expert will simplify complex scientific issues and help to educate you and the jury relative to these issues. Always help your expert find ways to simplify your defense theory and remember that Occam’s razor applies here, which is to say that the simplest explanation or strategy tends to be the best one. Metaphors are the best way to simplify otherwise complex scientific concepts, and you should work with your expert to create such metaphors to fit the facts of your case.
  • Plan both direct and cross-examination. It is probably best to avoid a plan to use specific or exact wording in the direct examination of the expert or in preparing the expert’s answers. This is because doing so inevitably creates a stilted or obviously rehearsed performance. Instead the goal is for you to spend enough time preparing the testimony of your expert that the performance appears to be spontaneous because in reality it is spontaneous.
  • Help your expert to anticipate cross-examination. Reverse roles with your meanest most tenacious prosecutor, and then cross-examine your expert as this prosecutor. Consider having a non-lawyer sit in on the preparation to offer his or her opinion about the clarity of the expert’s opinions and testimony. Modify the approach based on anything you or your assistant finds to be confusing or ineffective.
  • Instruct the expert witness to stay on topic and to not express any opinion on direct or cross-examination that is outside your theory of the case. It is also important that the expert not try to stretch his or her expertise and only to testify regarding matters upon which he legitimately has expertise. An expert that is shown to be unqualified in one area may be assumed to be unqualified in other areas and his or her credibility may be seriously questioned. There is nothing wrong with the expert expressing ignorance on a particular area, especially if it is an area that is not relevant to your defense theory.

Gas Chromatography in DUI Cases – Theory and Operation

By Patrick T. Barone

*From the upcoming 2010 update of Barone’s book, Defending Drinking Drivers

The process of gas chromatography involves the use of an instrument called a gas chromatograph (GC) to separate and analyze compounds that can be vaporized without decomposing the compound. Gas chromatography is particularly well suited to the separation of volatile organic compounds.

Human blood is a mixture of various substances and left alone, it is very difficult to analyze. However, some of the components of blood are volatile organic compounds, and the point of GC is to separate and analyze the volatile organic compounds that may be within the blood sample.

Thus, with the proper extractions procedures or for volatiles such as alcohols by use of a method called “head space,” various foreign components of the blood such as drugs, drug metabolites, and alcohols in blood can be measured and identified. In a drunk driving case we are primarily interested in the volatile ethyl (beverage) alcohol, but there are other potential volatiles of interest, such as acetone, which might be of interest where the driver was experiencing a diabetic episode.

Like all chromatographic methods, with gas chromatography there is a “mobile phase,” in this case a gas, which is used to carry the mixture over a “stationary phase.”  The gas is more fully called “headspace gas.”  With drunk driving cases, the stationary phase is typically a tube or capillary column.  The components in the mixture containing a driver’s blood leave this column in the order of their volatility, with the most volatile (first to vaporize) leaving the column first.

In the forensic lab testing blood for DUI cases, the gas chromatographic system might include the following:

  • The blood sample
  • The headspace vial
  • The internal standard
  • The carrier gas
  • The capillary column
  • The “oven”
  • The flame ionization detector (FID)
  • The computer
  • The printer

The capillary column is contained within an oven. The headspace gas is injected into the column and is measured as it come out of or “elutes” from the column.

Before an unknown volatile can be measured, it is important for the lab analyst to prepare a standard mix which usually includes several different volatiles including isopropyl alcohol, ethyl alcohol, methanol, acetone, acetaldehyde and toluene. This standard mixture allows the laboratory to determine the specific retention times of the various volatiles of interest.

Once the known standards mixture is tested with a specific column and the retention times recorded, the lab analyst can then use the gas chromatograph to qualitatively test unknown compounds.

A calibration curve is also produced in the laboratory.  This involves passing known quantities of alcohol through the column. The specific laboratory’s protocol will dictate how many different levels of alcohol are measured, but they will usually span from well below the legal limit to well above.  This calibration curve “tests” the column to be sure that it is capable of measuring specific known quantities.  Subtle changes in carrier gas flow; the flow of gases to the FID detector (if used) and subtle changes in the column are few of the reasons that the GC must be recalibrated very frequently.

Now that the column has been calibrated, the lab analyst is ready to begin the blood test.  The analyst starts by removing a very small amount of the driver’s blood from the blood draw vial and placing it, along with a very small amount of an internal standard, into a separate testing vial. This testing vial is called a “headspace” vial.  Internal standards are alcohols that would not be expected to occur in human blood except in minute quantities.  More importantly, the boiling point of these standards is different from the boiling point of ethanol.  This difference is important because it will result in a GC peak for the internal standard that is clearly distinguishable from the peak for ethanol. The internal standards that are typically used include n-propyl and t-butyl alcohol.

This headspace vial is then shaken to mix the chemicals and heated to produce the headspace gas. An injector system is used to introduce the sample to be tested into the GC column.  In the case of headspace method, a small amount of air (gas) above the liquid in the headspace vial which has become saturated with volatile components from the liquid sample is taken and injected into column via a micro syringe.  On its way into the headspace vial, the syringe passes through a rubber gasket.  With the headspace method no blood is directly being sampled because headspace testing involves an analysis of only the air above the blood sample.

Once the blood sample has been heated to produce the headspace gas, this gas is swept into and through the column by the carrier gas stream.  This phase is known as the mobile phase. A high pressure gas cylinder serves as the source of the carrier gas. There are several carrier gases that can be used, including helium, nitrogen and hydrogen.

Today, columns used in forensics are generally capillary columns up to 30 meters in length and are made of glass. The diameters of these columns are generally in the range of 0.25 mm. Modern capillary columns typically do not have “packings” as they once did but instead have a coating deposited onto the internal wall of the column. The capillary column consists of a solid support phase and a bonded liquid phase. In capillary columns, the solid support phase is the column itself.

The capillary column separates the sample into its component parts. The oven helps control the speed and amount of separation. The detector detects the presence of and can measure the amount of the volatiles as they exit out of the column. A common detector used in GC systems is the flame ionization detector (FID). However there are many other detectors that are used for special detection requirements.

The FID is located at the end of the column. Because the volatiles involved are flammable, they can be burned in the flame ionization detector.  Thus, as the chemicals exit or “elute” from the end of the column the FID incinerates them, and this combustion produces an electronic charge in the form of ions.

These ions are then measured by the detector and subsequently converted by the instrument’s computer into a graph which usually contains two peaks. One of these peaks represents the internal standard and the other the ethyl alcohol.  The retention time of the peak for the ethyl alcohol must match the expected retention time in order to qualitatively confirm its identity. The expected size and retention time of the peak for the internal standard will be known because of prior testing and because a precise amount of it was placed by the analyst into the headspace vial.  The area beneath this peak, called the “area under the curve” is compared with the peak for the ethyl alcohol.  This ratio is compared with the calibration curve and converted into the driver’s blood alcohol level.

Swimming Pool Metaphor

Perhaps some of the qualitative aspects of GC blood testing can be more fully understood metaphorically.  Think of an Olympic swimming competition where at the beginning of the competition all the swimmers are anonymous. Your goal in this fictitious competition is to figure out the identity of the swimmers. As usual, at the beginning of the race the swimmers all begin at the starting line and as the race begins the swimmers jump into the pool and quickly begin to separate as they race toward the finish line.

While you watch the competition unfold the same event is repeated over and over again and you see the same swimmers compete against each-other several times.  As you watch you begin to notice that the each individual swimmer seems to finish each race at the same time.  If you were keeping notes of each individual swimmer’s time, pretty soon you’d be able to identify the swimmer based on the amount of time it took him or her to finish the race.

Similarly, in the world of GC, the volatile organic compounds finish the “race” at different rates depending on their various chemical and physical properties and their interaction with a specific column.  The volatiles are qualitatively identified based on the amount of time it takes to finish the “race” to the GC’s detector. In gas chromatography this is what happens when the lab analyst runs the standards mixture and records the time the various volatiles elute from the column. This is the qualitative part of gas chromatography, and answers the question “what am I.”

To carry our metaphor a step further, the swimming pool would be similar to the column in the GC.  The solid phase is a bit like the water in the swimming pool in that the water creates a resistance against which the swimmers must race through as they continue toward the finish line.  This resistance helps to separate out the fast swimmers from the slow swimmers, and this separation makes it easier to determine the swimmer’s identity.

Proven Drunk-Driving Jury Argument

From Attacking and Defending Drunk Driving Tests by Don Bartell

In 2007 the California DUI Lawyers Association in conjunction with the National College for DUI Defense released the results of a DUI jury research project. The two principal goals of the project were to discover what jurors were most receptive to DUI defendants [see Chapter 19], and what arguments resonated best with jurors in a drunk driving trial. The study showed that one of the best arguments resonating with jurors was the failure of the police to follow proper guidelines. Make sure the heart of your case is about attacking the government’s mistakes – not defending your client’s.

Some of key findings from the jury research project revealed the following:

  • The rising blood alcohol defense did not resonate particularly well with jurors. The defense is slightly complicated to present, and basically is telling the jurors that the officer stopped the defendant before the defendant had a chance to become drunk. This is not the strongest argument to make people root for you.
  • Many defense lawyers have long advocated that defense attorneys describe breath testing equipment as machines. After all, machines do break. By the same token, prosecutors have been instructed to call breath machines instruments. An instrument seems much more precise. People describe surgery being done with instruments, not machines. In court, these conflicting designs sometime turn humorous. The lawyers try to outdo each other: one calling the device a machine, the other characterizing the device as many times as possible as an instrument. As it turns out, the results of the jury research project recommended that the defense describe breath testing equipment as neither instruments nor machines. The feeling from the project was that the word machine, like the word instrument, has a certain feeling of accuracy to it. The results of the project recommend that defense lawyers instead describe breath testing equipment whenever possible in general terms. Describe the end results, calling them for instance, evaluations. Given this, consider calling the breath machine, in court, the breath evaluator.
  • Instead of using the term margin of error, the jury project recommended defense lawyers describe the margin of error in alcohol testing devices as a range. Combining the lessons together, one might ask, Isn’t true that this breath evaluator has a blood alcohol range of plus or minus .02%?
  • As for field sobriety tests, the project suggested calling them preliminary roadside evaluations. The research project also found that field sobriety tests not done in conformity with the NHTSA guidelines caused significant concern for jurors. [See the CD that accompanies this book for a NHTSA manual.] Consequently, emphasize the failure to properly follow police procedures. Cases are about what cases are about.

Donald Bartell is a partner in the law firm of Bartell & Hensel in Riverside, California, and has been in private practice since 1984. He is on the Board of Directors of the California DUI Lawyers Association, and is a frequent lecturer around the state on DUI trial tactics. He has been asked to participate in the California DUI Lawyers Association and National College for DUI Defense’s jury research project investigating what arguments resonate with jurors in drunk driving cases.

Single-Page Checklist of Recurring DUI Objections

From Attacking and Defending Drunk Driving Tests by Don Bartell
Voir Dire

  • The question does not go to cause or to assist in the exercise of peremptory challenges.
  • The juror was improperly struck due to race/sex in violation of the 5th and 14th Amendments to the U.S. Constitution. [See in Court Batson Reference Guide Chapter 19.] Also consider state objections.

Opening Statement

  • Argumentative.


Police Officer

  • Leading.
  • Calls for a narrative.
  • No Foundation/Beyond the Officer’s expertise.
  • Speculation.


State Percipient Witnesses

  • Leading.



  • No Foundation as to qualifications or to procedures used.


State Expert Witness

  • Chain of Custody.
  • No Foundation.
  • Not an expert in this area (sometimes occurs with respect to FST’s).
  • Improper Hypothetical (no facts to support hypothetical).
  • Non-responsive.
  • Hearsay and violates the defendant’s right to confrontation under the Sixth and Fourteenth Amendments to the United States Constitution.


Defense Percipient Witnesses

  • Argumentative (cannot ask the witness to comment on another witness’ veracity).


Defense Expert

  • Request the Court to allow the witness an opportunity to finish his/her answer.


The Defendant

  • Argumentative (cannot ask the defendant to comment on another witness’ veracity).
  • Request the Court to allow the witness an opportunity to finish his/her answer.
  • Violates the defendant’s rights to remain silent under the 5th and 14th Amendments to the U.S. Constitution. The question constitutes Doyle v. Ohio error. Request the Court to admonish the jury to disregard the prosecutor’s question.


Closing Argument

  • Misstates the evidence / misstates the law.
  • Vouching, improperly stating personal opinion.
  • Violates the defendant’s right to remain silent under the 5th and 14th Amendments to the United States Constitution. Griffin v. California error (commenting on the defendant not testifying); Doyle v.Ohio error (commenting on post Miranda silence). Request Admonishment.
  • Improperly appeals to passions and emotions of jurors.

Donald Bartell is a partner in the law firm of Bartell & Hensel in Riverside, California, and has been in private practice since 1984. He is on the Board of Directors of the California DUI Lawyers Association, and is a frequent lecturer around the state on DUI trial tactics. He has been asked to participate in the California DUI Lawyers Association and National College for DUI Defense’s jury research project investigating what arguments resonate with jurors in drunk driving cases.

Slides to Use When Voir Dire in a DUI Case Is Limited

From Innovative DUI Trial Tools by Bruce Kapsack

With the increase of limited voir dire, it has become incumbent upon counsel to be prepared to ask quick, simple questions in order to pick a jury. While I do not favor allowing this trend to continue or expand (see the arguments in the beginning of this chapter) I am familiar with reality. The following power point slides were developed based on ideas from Robert Hischorn to deal with this problem.

These are not inclusive and should be a good starting point for your own adaptation and use. Add more specific questions that relate to the issues in your particular case.

Simply put one up on a screen or poster board and ask each juror to give his or her numerical position. After every three or four jurors, re-read the question aloud to stop an avalanche of following the answer given by the preceding person. Either you—or even better, your client—can input the score for each juror. The higher the score, the better the juror.

This can be done so quickly that the prosecutor is not able to keep up. And the prosecutor will not necessarily know that jurors with the low scores are the ones that he or she wants.

The beauty of this system is, by creating a simple score card to record the number of the answer chosen by each juror, you can tell who you do and do not like. Be sure to draft all your questions the same way so that the higher numbered answers reveal jurors with attitudes that are favorable to the defense. Thus, the higher the total score, the more favorable the juror. It will not help you if good jurors get ones on some questions and sixes on others.

View PDF slides below (from Innovative DUI Trial Tools)

Fig. 2-01 Burden of Proof

Fig. 2-02 Guilt Based on Being Charged

Fig. 2-03 Guilt Based on Chemical Tests

Fig. 2-04 Guilt Based on Defendant’s Not Testifying

Fig. 2-05 Trustworthiness of Chemical Evidence

Fig. 2-06 Trustworthiness of Officer’s Opinion

Fig. 2-07 Guilt Based on Two Drinks

Fig. 2-08 Better to Free the Guilty Than Convict the Innocent

Fig. 2-09 Field Sobriety Tests and Ability to Drive Car

Fig. 2-10 Field Sobriety Tests and Ability to Judge Blood Alcohol Level

Bruce Kapsack originated many of the DUI defense strategies used throughout the country.  He has worked or lectured with virtually every nationally-known expert in the DUI arena, and his DUI lectures for the California State Bar and the California Public Defenders are among the best attended in the state. Mr. Kapsack is an Instructor of NHTSA’s Standardized Field Sobriety Tests.

Attacking Widmark Calculations

From Attacking and Defending Drunk Driving Tests by Don Bartell

The more the defense lawyer can shake jurors loose from the predisposition of guilt (the predominant problem in a drunk driving trial) the more favorable the trial prospects of the defense.

Attacking Widmark calculations is an effective way to accomplish this mission because the Widmark formula uses averages to arrive at conclusions. Most jurors understand the problems inherent with using averages, and averages are the antithesis of proving something beyond a reasonable doubt.

When jurors hear that there is going to be a calculation using a long established formula, most jurors presume that the calculation is going to have some type of mathematical certainty.

However, when the jurors hear that in reality the Widmark calculations are actually nothing more than an educated guess, hopefully they will begin to question some of their initial assumptions. After the cross-examination on Widmark calculations, many jurors may not be as predisposed to convict as when they were first seated. The defense campaign from the start is to get jurors to think “there is more to this than I thought—the case is not cut and dried.”

One way to remind jurors about the problems with averages that are used in Widmark calculations is to give them analogies that emphasize the problem with using averages. There are an endless amount of examples. For instance, you might tell jurors if one leg on a man’s pants is too short, and one leg is too long, the prosecution’s tailor would have you believe that on average the pants fit just fine. Or, if when you first turn the shower on in the morning, the water is biting cold, and then it turns to scalding hot, don’t worry, on average according to the prosecution’s plumber you are having a pleasant shower.

It is difficult to describe, but you will sense a perceptible change in the courtroom when the presumption of guilt starts to fade. Jurors seem more attuned to your questioning; the judge seems to give you more leeway in your cross-examination; the prosecutor seems a little more on edge. The difference is that the predominant problem in the case is beginning to become solved. This is the secret to winning drunk driving trials.

Attacking the Calculations

In a typical drunk driving prosecution, at some point the state’s expert will give an opinion as to how much the defendant had to drink. The prosecutor will ask the expert to assume a certain time of driving, a weight of the defendant, and give the expert the chemical test result.

The expert usually takes out a calculator and performs some intricate calculations. It looks serious, and with the expert’s deep-studied concentration while performing the calculations, it is an impressive show to the jury. There is some suspense while the jury waits for the result.

The result is frequently at odds with what the defendant told the police officer he or she had to drink on the night in question. The prosecutor then plays this point up to the jury.

Note, however, that usually nothing more is offered in the way of how this result was actually obtained.

Expose the Charade

With the aid of a calculator, an expert has determined that your client had a high BAC. This conclusion further cements the jurors’ initial impressions that the defendant is in fact guilty. After all, an expert for the state has just as much as said so.

However, the way that these Widmark computations are presented provides a unique opportunity for the defense.

Ask the state’s expert if he or she discussed the case with the prosecutor before testifying. The answer is almost always yes. Then ask if the two of them discussed the calculations determining the number of drinks the defendant consumed. Again the answer is usually yes. Now draw on the fact that the expert knew the answer to the prosecutor’s drink calculation question before it was asked. Do this by asking (telling) the expert that since the expert already knew the answer to the question before it was asked, the drama staged by taking out the calculator was nothing more than an unnecessary charade for the jury. The following is a sample cross-examination:

Q:    Did you discuss this case with the prosecutor before coming to court?

A:    Yes, I did.

Q:    And as part of that preparation did the two of you discuss how much you believed the defendant had to drink?

A:    Yes.

Q:    You determined that by performing the calculations you just did for us in court today?

A:    I used the same method.

Q:    Then I take it prior to testifying today you knew the answer to the question as to how much you believed the defendant had to drink?

A:    Yes.

Q:    So taking your calculator out and spending all that time performing computations was not necessary?

A:    Well, I like to be accurate.

Q:    You knew the answer already—your computation was nothing more than a charade you performed for the jury?

At this point, you really do not care what the answer is. The witness and the prosecutor have been exposed. If you are lucky, someone seated nearby in the jury box might begin to start thinking, if the case is so “cut and dried,” why is the prosecution going to such lengths to deceive us. The predominant problem for the defense is beginning to become solved.

There is not much downside risk in this line of questioning. If the witness denies going over the calculations with the prosecutor before testifying, you can simply move on to other questions. No one will know the significance of what you were about to ask, but did not. Also, the jury may think it is a little sloppy for the prosecution to put a witness on the stand without discussing the case with the witness first.

If you are still concerned about venturing into this area without more assurance of a positive reply, then watch the prosecutor and the expert during any recess. It is a common practice to have a recess before the prosecutor puts on the state’s expert. Generally, the police officer is the first witness to testify, followed by the expert. After the officer’s testimony, it is a natural time for the court to take a recess. Some prosecutors even ask for the recess so they can talk with their expert. You can sometimes see the expert and the prosecutor doing the computations with the calculator in plain view in the hallway or at the counsel table during the recess.

Ask What the Formula Is

Many experts do not really have an expert understanding of Widmark’s work. What they count on is that you do not have much of an understanding of the work either. They presume that they can get away with making Widmark calculations without discussing the limitations in the calculations, and usually they do.

You can expose imposters posing as experts on Widmark. Ask the expert if there was some formula the expert used to calculate the amount of drinks the expert claims the defendant drank. The expert will reply that there is such a formula. Ask if the formula used was the Widmark formula. The expert will say yes, or will say a modified version of the formula based on Widmark’s work was used. Either way the inquiry proceeds in the same manner.

Next ask the expert what the Widmark formula is. Many experts will reply with a formula that is not the actual formula. These experts, instead, use a shorthand version of the formula in court. This shorthand version of the formula does not accommodate any of the variables that are in the actual formula. [For the actual formula, see Chapter 9, Blood Alcohol Concentration and Widmark Calculations.]

The shorthand formulas experts predominately use are as follows:

  • Number of drinks, times 3.75, divided by your client’s weight, minus .017% an hour = BAC
  • Or solving for the alcohol level per drink they use the following formula: BAC/drink = 2.57/(weight) (Widmark r)]

When the expert gives a reply with a formula that is not Widmark’s formula, ask the expert “this is not the actual formula is it?” The expert will then realize that you have more information on this topic than he or she expected. Only now will this expert own up to the fact that the version of the formula they gave is not actually Widmark’s formula. Finally, ask the expert what the actual Widmark equation is. Stunningly, the answer is often that the expert does not know.

You can emphasize in closing argument that the expert made calculations without knowing the actual formula.

Ask Whether the Expert Has Read Widmark

Most experts have not read Widmark’s work.

If you ask an expert if he or she has read Widmark’s work, they may reply smugly that they have not read it because the work is in German. However, do not let the expert escape so easily. There is an excellent English translation of the work by Randy C. Baselt, Ph.D.

Prior to actually asking the expert if he or she has even read Widmark’s actual work, ask a series of questions from the work. Let the expert answer “I do not know” a few times before asking the ultimate question: “Have you even read the book?” This will help maximize the impact of their failure to read the definitive work.

If the expert does not know the actual formula, and has not even read the book, the strength of the expert’s opinions and calculations will be diminished. The following is a sample cross-examination of a criminalist’s knowledge of Widmark’s work:

Q:    These calculations you did to determine the amount of drinks the defendant consumed, did you use some type of formula?

A:    Yes.

Q:    Is that the Widmark formula?

A:    Yes.

Q:    Well, could you please tell us the Widmark formula?

A:    I would be happy to. The formula is the number of drinks, times 3.75, divided by your client’s weight, minus .02% an hour.

[Expert’s frequently use a burnoff rate of .02% an hour for no other reason than it makes calculations in court easier. The actual average rate is lower, although, the normal range extends beyond this point as well.  Some experts calculate the formula by finding for the blood alcohol level per drink. They use the following formula: BAC/drink = 2.57/(weight) (Widmark r).]

Q:    Is that the actual formula?

A:    No, it’s a version I use for court. It is quicker so we don’t waste the jury’s time.

[The witness will sometimes offer up some diversion hoping to avoid the next question. The examiner should simply make a mental note that the cross-examination appears to be working. Then plow straight ahead with your questioning.]

Q:    Well what is the actual formula?

A:    I do not know. This is the one we use.

[The witness realizes he or she has been caught and tries to drag others down with the witness by using the word “we.”]

Q:    Well, let me ask you this. You told the prosecutor on direct examination that the odor of an alcoholic beverage was one of the factors you used to base your belief that the defendant was impaired.

A:    It was one factor.

Q:    Didn’t Doctor Widmark indicate in his book that the odor of an alcoholic beverage is of a little assistance in determining if a person is under the influence?

A:    I would agree with that.

[This is a dodge to avoid answering the question of whether or not the expert knows what is in Doctor Widmark’s book. The witness would be better off acknowledging right away that he has not read the book. But the witness is still hopeful the question will never be presented.]

Q:    Do you know what Widmark found the coefficient of variation to be for men concerning the constant r factor?

A:    No.

[The answer is 13. Again, if the witness had answered on his or her own that the witness had not read the book, the questions would have already ceased. Failure to do so prolongs the agony.]

Q:    Well how about for women, what was the coefficient of variation for the r factor for them?

A:    I do not know.

[The answer is 10.]

Q:    Well, let me ask you this, how many men and women did Widmark use in his chapter on study of the kinetics of the conversion of alcohol, to determine the r factor?

A:    I do not know.

[The answer is 20 men and 10 women.]

Q:    Did Doctor Widmark find any correlation in his work between the constant ß and the constant r?

A:    I do not know.

[The answer is he did not find any correlation.]

Q:    You will forgive me, but have you read Widmark’s work?

A:    No, it is written in German.

Q:    Well have you read the English translation by Randy Baselt, Ph.D.?

A:    No.

Q:    You have not read any version of Widmark’s original work?

A:    No.

Donald Bartell, author of Attacking and Defending Drunk Driving Tests,  is a partner in the law firm of Bartell & Hensel in Riverside, California, and has been in private practice since 1984. He is on the Board of Directors of the California DUI Lawyers Association, and is a frequent lecturer around the state on DUI trial tactics. Mr. Bartell is a contributing author to James Publishing’s California Drunk Driving Law, and wrote the chapter Defense of Drug Cases in Medical-Legal Aspects of Drugs.

Use the Police Report to Hog-Tie the Officer

From Relentless Criminal Cross-Examination by Kevin Mahoney

Early in my career a trial lawyer told me, “The answer is in the documents,” and it has proven true so often that I consider it Gospel. I scrutinize the documents. I read the important documents again and again and again. I commit them to memory. I compare them against other documents and, if available, transcripts of the author. I look to see when they were written to determine the order in which they were written. I analyze not only what is written, and how it is represented, but what is missing. Use these documents to pin the witness to the mat.

Police Report Not Objective

Many attorneys review police reports to discover what happened. A police report is not an objective recitation of the facts from a disinterested witness. Instead, it is usually written by the arresting officer post-arrest. Most officers write a report not with the goal of helping the arrestee obtain an acquittal, but to make the arrest stick; to safeguard the fruits of a constitutionally suspect search; to satisfy a supervisor that the arrest was justified; or to provide the prosecutor with a summary of the “facts.” If they have previously testified or have been schooled in drafting reports, they may write the report to minimize their exposure on cross-examination. They will carefully select their words. They may twist the words of witnesses, misrepresent what the client said or how he said it, and deliberately leave out exculpatory evidence. If they have made similar arrests in the past, for DWI for example, they may simply reuse the same “facts” or phrases, either out of habit or laziness. Few jurors will have considered what factors motivate a detective or officer in drafting his reports. Use cross-examination to both expose the officer’s motivations and to educate the jury about them.

Pattern Cross: Pressure to Draft Comprehensive Report

It is not uncommon for an officer or detective to testify to an important “fact” not included in his report. If questioned on his failure to note the “fact” in his report, an experienced officer will typically shrug it off with, “This is only a summary, Counselor. It doesn’t include every detail or every observation.” If left unchecked, on redirect this officer might decide to sneak additional “facts” into his account. Worse, officers who have not yet taken the stand will hear how easy it is to slip some additional “facts” into their testimony. Corner the officer by highlighting the pressures on the officer to make his report as comprehensive as possible.

Officer taught at Academy to draft comprehensive reports

Q:  Officer, you attended the Police Academy?

A:  That’s correct.

Q:  At the Academy, you were taught the importance of drafting police reports?

A:  Yes.

Q:  That the report should include all important facts?

A:  Well, again, Counselor, it is a summary.

Q:  You were taught that a report should include all important facts?

A:  It’s only a summary, as I’ve said.

Q:  Okay. The Academy actually gives a course in drafting a police report?

A:  Yes.

Q:  At the Academy, you were taught that other officers or detectives might rely on your report in conducting their investigations?

A:  That’s correct.

Q:  That these detectives or officers require all the important information to do a proper investigation?

A:  Yes.

Q:  And for that reason, your report should be comprehensive?

A:  Well, my report includes the necessary information.

Q:  For that reason, your report should be comprehensive?

A:  Ah… yes.

Officer drafts report for benefit of prosecutor

Q:  You were taught that the prosecutor will be provided with your report?

A:  Yes.

Q:  To familiarize himself with the case?

A:  Yes.

Q:  And rely on that report to make a bail argument?

A:  Right.

Q:  To inform the court of exactly how strong the evidence against the defendant is?

A:  Yes.

Q:  To allow the prosecutor to assess the likelihood of securing a conviction?

A:  Yes.

Q:  To, perhaps, negotiate a plea with the defense attorney?

A:  Yes.

Q:  To prepare for trial?

A:  Yes.

Q:  Which includes preparing a direct examination?

A:  That’s right.

Q:  Of you?

A:  Yes.

Q:  And you’ve learned that, prior to the trial, you may have little or no contact with the prosecutor?

A:  Unfortunately, that’s true.

Q:  You might meet with the prosecutor for the first time the morning of the trial?

A:  Yes.

Q:  And in such a case, much of what a prosecutor learns about your arrest he will glean from your report?

A:  Yes.

Q:  And for that reason alone, your report should be comprehensive?

A:  As I said…

Q:  To make sure that the prosecutor is properly prepared, you’ve learned that your report should be comprehensive?

A:  Yes.

Q:  When drafting your report, you make sure you include everything you want the prosecutor to know about your case?

A:  Well, I try.

Q:  And you’ve learned that sometimes six months, a year, or more might pass between the arrest and the trial?

A:  Correct.

Q:  And during that six months or more, you’d expect to make additional arrests?

A:  Yes.

Q:  To testify in other cases?

A:  Yes.

Report drafted when events and memory are fresh

Q:  And like all of us, your memory immediately following an event is better than it is six months or more after the event?

A:  That’s true.

Q:  You were outside the courtroom this morning?

A:  Yes.

Q:  You were seated on the bench just outside this courtroom?

A:  Yes.

Q:  Reading your report?

A:  Ah, yes.

Q:  Reading your report to refresh your memory?

A:  Yes.

Report drafted in anticipation of cross-examination

Q:  When drafting your report, you include everything that you will want to remember when the trial rolls around?

A:  Yes.

Q:  You are also aware that the defense lawyer will receive a copy of your report?

A:  Yes.

Q:  You know from testifying in other cases that the defense lawyer will cross-examine you on the contents of your report?

A:  Yes.

Q:  That’s another reason you were re-reading your report?

A:  Well, I… that’s true.

Q:  You know from experience that if you testify to an allegation not contained in the report, the defense attorney will question you about that during cross-examination?

A:  Yes.

Q:  That’s happened before?

A:  Yes.

Report is “complete summary” of all important facts

Q:  You wrote the report yourself?

A:  Yes, of course.

Q:  You had the time necessary to draft the report?

A:  Yes.

Q:  You’re not given a time limit?

A:  What do you mean?

Q:  In other words, you’re not given 10 minutes to draft a police report?

A:  No.

Q:  You take the time you need to draft the report?

A:  Within reason.

Q:  When you finished the report, you read it to yourself?

A:  Yes.

Q:  You were satisfied that it included every important fact?

A:  As I said, it’s a summary.

Q:  You were satisfied that your report included every important fact?

A:  It was a summary.

Q:  A summary that did not include every important fact?

A:  Yes.

Q:  So, you provided the prosecutor with an incomplete summary?

A:  No.

Q:  In preparation of your testimony here today, you re-read an incomplete summary to refresh your memory?

A:  Ah, no.

Kevin J. Mahoney is a criminal defense lawyer in Cambridge, Massachusetts. He regularly provides on-air legal analysis for Fox News Live, Fox & Friends, CNN, Nancy Grace, and Court TV. His successful defense of Christina Martin, dubbed the “Jell-O Murderer” by the national press, was chronicled on Court TV’s Forensic Files. Mahoney has won 36 of his last 38 trials.


Defending Drinking Drivers
by Patrick Barone

Federal Forfeiture Guide
by Frank Bowman and Roger Haines

Federal Prison Guidebook
by Alan Ellis and J. Michael Henderson


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