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.


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