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DUI Defense

Direct Examination: Curve Expert

CV and Expert Qualifications:

  • Please describe your educational background; degrees; certifications; titles
  • Describe work history
  • Publications  (Exhibit #1- curriculum vitae).
  • Have you testified before?
  • How many times?
  • How often testify for defense?
  • Ever testify for State?  (If could provide helpful testimony, would you)
  • Will you be receiving payment for your testimony today?  How much?
  • Will you receive any other amount?
  • Does who hires you influence how you evaluate a case?
  • Ever tell defense attorney you can’t provide helpful testimony for his or her client based upon your analysis?

Physiological Effects of Alcohol:

  • Explanation of the physiology and pharmacology of alcohol in human being.
  • Please explain some commonly used terms:

-Absorption/rate of absorption;

-Distribution/distribution ratios;

-Elimination of alcohol;

-Alcohol concentration curve 

  • Please explain the process of how ethyl alcohol effects a person.

-Start from ingestion of the alcohol to when it reaches the brain.

-Explain the process/time periods associated with that.


Absorption of Alcohol into the Bloodstream:

  • Takes finite period to go into blood stream -- delayed absorption - 1 and 1/2 hours to be absorbed :

-Food make a difference in absorption of alcohol.

-Explain how food makes this difference 

(With food present, 90 minutes or more for absorption of ethanol; fatty foods do prolong this time.  The stomach is not efficient for absorbing materials, absorption takes place primarily in small intestine.  Food in the stomach delays movement of material into the small intestine.  That is why presence of food is so important determining absorption of ethanol.)

  • Absorption, distribution and elimination are separate processes that occur at the same time =

-Contemporaneous – not mutually exclusive.

-If eat sizeable amount, is absorption slowed down?


Formula for Determining BAC:

  • Is there a formula that is medically and toxicologically accepted for the purpose of determining the BAC of an individual at a particular point in time.

-Law enforcement rely on this formula

-Exhibit #2:   Basic Training Program for Breath Examiner Specialist

-Endorsed by - WI State Patrol – pp.

-Pages are identical to book 


Determining the Defendant's BAC at Specific Time and Date: Curved BAC

  • Based upon your training and experience, have you determined the blood alcohol concentration of [the DEFENDANT] on the [DATE and TIME that defendant was stopped, operating vehicle]

-Show Exhibit 3 -  Does this report accurately reflect how you determined [DEFENDANT’S] BAC?

-What was [DEFENDANT’S] blood alcohol concentration at the time of driving based on his drinking history?

-[DEFENDANT’S CURVED BAC]: is that is less than .08?

-Explain how you determined that [DEFENDANT’S] BAC was [CURVED BAC]?


-Number of drinks consumed by DEFENDANT

-When did the [DEFENDANT] consume the first drink?

-When did the [DEFENDANT] consume the other drinks?

-When did the [DEFENDANT] consume the last drink?

-What kind of drinks were they? (e.g., alcohol content)

-How large were the drinks?

-Food consumed by DEFENDANT


-What kind?

-How much?

[Note: The expert should look at all relevant variables that may have affected the client’s BAC.  These may include, Gender, Weight at time of arrest, History of liver/stomach disease or surgeries, detailed history of what the subject drank, the volume consumed, and the time of each drink, detailed history of meals/snacks eaten from three hours prior to consuming alcohol up to and including the last drink consumed, Time of arrest, Time of and type of test used, Medications consumed, Dentures/crowns/piercings.  This list is not exclusive.]

-You testified that [DEFENDANT’S] BAC at [TIME OF OPERATION; STOP] was [CURVED BAC].  Is that an opinion that you hold to a reasonable degree of scientific certainty?

If Defendant Also Had Prescriptions Medications in Blood:

  • Are you aware that DEFENDANT was on medication at the time?

-What was he on?

-Either of these medications impact how the alcohol [DEFENDANT] consumed was absorbed or metabolized? 

-Just to be clear, did either of these medications affect his BAC concentration?

-Either of these medications effect his fine motor function?

-Affect his hand/eye coordination?

-Affect his large motor function?

-Affect his ability to safely handle and control a motor vehicle?

  • Is that an opinion that you hold to a reasonable degree of scientific certainty?

DEFENSE ATTORNEY now offers and moves into evidence Exhibits indicating calculations/actual BAC at time of operation.

State's Expert's Use of Reverse Extrapolation to Calculate BAC:

  • There has been testimony from State’s expert about reverse extrapolation.  He used reverse extrapolation of the blood test result of [BAC that STATE expert calculated with REVERSE EXTRAPOLATION] to determine that [DEFENDANT’S] BAC at the time of driving was __________.

-Would the State’s expert calculation be accurate? 

-Reverse extrapolation only takes into account elimination & does not account for absorption

-[DEFENDANT] had absorption going on through ___ p.m, so reverse extrapolation not reliable

-Is the calculation of the State’s expert speculative?

The state often tries to use reverse extrapolation to convict a defendant.    This is totally unreliable during any time absorption is still continuing (up to 1 ½ hours after the last drink is consumed).  To argue against reverse extrapolation of prosecution case: stipulate the blood test result is accurate and use that along with evidence of absorption rate and curve analysis.

-Is that an opinion that you hold to a reasonable degree of scientific certainty


  • Would a person's fine motor function be impaired at a [DEFENDANT’S CURVED BAC]? 
  • Would a person's hand/eye coordination be impaired at a [DEFENDANT’S CURVED BAC]?
  • Would a person's large motor function be impaired at [DEFENDANT’S CURVED BAC]?
  • Judgment re: would a person with a BAC of [DEFENDANT’S CURVED BAC] be able to safely handle and control a motor vehicle?
  • Hold an opinion to a reasonable degree of scientific certainty as to whether or not [DEFENDANT], at a [DEFENDANT’S CURVED BAC] was impaired on [DATE OF STOP; ARREST] at [TIME OF DRIVING, STOP] as a result of his consumption of alcohol?

The Daubert Standard

The Daubert standard is a rule of evidence that requires the proponent of the expert evidence to show that it is reliable.  Specifically, the proponent of the expert evidence must prove by a "preponderance of the evidence" that:

  1. It is based upon sufficient facts or data.
  2. The methods used to reach conclusions are based upon reliable principles and methods.
  3. The principles and methods are applied reliably to the facts of the case.

Three cases which make up the Daubert standard are: Daubert v. Merrell Dow Pharm., 509 U.S. 579 (1993); General Electric Co. v. Joiner, 522 U.S. 136 (1997); and Kumho Tire v. Carmichael, 526 U.S. 137 (1999).

In 2011, Wisconsin amended its expert evidence statute, Wis. Stat. § 907.02, to comport with the Daubert standard.  The Daubert standard applies to all actions (criminal and civil) filed in Wisconsin on or after February 1, 2011.

Click here for more information on the Daubert standard.


DNA Analysis

Deoxyribonucleic acid (DNA) is a molecule containing a species' biological blueprint.  DNA is made up of a sequence of four bases: adenine (A), cytosine (C), guanine (G), and thymine (T).  All humans have approximately 99% of the same sequence of As, Cs, Gs, and Ts.  It is the other 1% that makes each person unique, and in turn, what makes DNA powerful evidence in support of guilt or innocence.

The first step in addressing DNA evidence is to get the lab reports.  This checklist and sample discovery demand were created to help attorneys/litigants identify whether they have all of the lab reports associated with DNA evidence.

There are different types of DNA tests, such as Short Tandem Repeates (STR), Mini-STR, Y-STR, and Amelogenin (gender typing) testing.  The probative value of the test results depends in part on the test itself as well as the biological material(s) that was tested.

For more information on DNA and DNA testing please see DNA for the Defense Bar, a guide to better understanding DNA and how to litigate DNA issues that was written for defense attorneys by defense attorneys and DNA experts.

Eyewitness ID

Eyewitness ID testimony differs from other types of forensic testimony in that it is typically elicited from non-experts (i.e., victim, witness, and/or police officer(s) administering a line-up). The testimony is often personal, emotional, and particularly powerful, especially if unchallenged.

Social science research has shown that eyewitness ID is often unreliable. According to the Innocence Project, "eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in nearly 75% of convictions overturned through DNA testing." Such findings underscore the point made on page 127 of the National Academy of Sciences Report, Strengthening Forensic Science in the United States: A Path Forward, that "effective use and interpretation relies on scientific knowledge and continuing research."


Variables affecting the reliability and/or validity of an eyewitness ID is often broken up into two parts: 1) General Impairment Factors (Estimator Variables), and 2) Identification Tests (System Variables).

General Impairment Factors (Estimator Variables) are innate and unchangeable factors that affect every person and identification to varying degrees. These include:

Environmental factors (i.e., lighting, distance between witness and assailant, and time).

Stress - negatively affects a witness's observational skills, which is contrary to common notion that stress sharpens a person's focus.

Memory - factors affecting memory include, but are not limited to, the passage of time since the event, confirmation bias, and the stress associated with witnessing or experiencing a traumatic event.

Weapon focus - the presence of a weapon distracts the victim's focus from the assailant.

Identification Tests (System Variables) are changeable and can be controlled by the criminal justice system through the implementation of procedures and following best practices. Important system variables include the type of line-up used and how it was administered.

In April 2010, the Wisconsin Department of Justice (DOJ) created a Model Policy and Procedure for Eyewitness Identification.


Depending on the case, a challenge to an eyewitness identification could take place pretrial, during trial, or both. Regardless, it is important to get into evidence the social science research. This can be done through the learned treatise statute and/or expert testimony.



Friction Ridge Analysis

Friction ridge analysis (fingerprints, palm prints, footprints, etc.) has been a staple in the criminal justice system. Recently, however, some if the most prestigious scientific organizations in the world, such as the National Academy of Sciences and the American Academy of Forensic Sciences, have called into question the reliability and validity of friction ridge analysis.

The first step in addressing friction ridge evidence is to get the evidence.

Click here for a sample discovery demand intended to provide a blueprint for attorneys to get the materials needed to effectively litigate friction ridge analysis issues.

Friction ridge analysis was once though infallible. Experts testified about "zero error" and some will continue to do so if unchecked. However, such claims are not supported by fact.

ACE-V (Analysis, Comparison, Evaluation, and Verification) is the technique used to analyze latent prints. An examiner will ultimately offer one of three conclusions: identification, exclusion, or inconclusive. ACE-V is a loose framework for latent print analysis. The ACE-V method says very little about the standards used by a particular examiner to analyze a print. Even at its best, the ACE-V method does not eliminate:

Human Error -- the ACE-V process relies on human skill and interpretation at every step. The veracity of the opinion is dependent on a variety of factors such as the skill of the individual examiner(s), quality of the latent print, and procedure used.

Bias -- outside factors and/or preconceived notions may unintentionally influence an examiner's opinion. Please see the section on cognitive bias for more information.

Problems with Repeatability -- the subjective nature of friction ridge analysis does not easily allow for replication. Different examiners may have different opinions as to the quality of the latent print or the number of similarities between the latent print and known print.

Error rate is one measure of reliability. Although a "zero error rate" does not exist, the actual error rate for friction ridge analysis is unknown. Research is currently being undertaken to address this issue.


There are many different ways to address friction ridge analysis. Each case is different and what is best in one case may not be in another. Whatever strategy or strategies you decide should fit into your theory of defense. Here are some examples of how to challenge friction ridge analysis.

Cross Examination -- a simple, yet effective, way to challenge friction ridge analysis is through cross examination of the state's witnesses. Expert testimony is not always needed to get your points across. Did the state's expert follow the recommended procedures of the scientific working group SWGFAST? In lieu of expert testimony, you can attempt to use scientific reports that are critical of friction ridge analysis as direct evidence through Wisconsin's Learned Treatise Rule. Click here for a sample motion.

Daubert Challenge -- friction ridge analysis has withstood Daubert challenges in other jurisdictions. Instead of generally challenging the forensic evidence as unreliable, a better option might be to challenge the principles and methods used by the specific examiner.

Expert Testimony -- sometimes you may want to have an independent examiner review the evidence and offer an opinion.

Forensic Sciences Practice Group

The 2009 National Academy of Sciences (NAS) report “Strengthening Forensic Science in the United States: A Path Forward” concluded, “[L]awyers and judges often have insufficient training and background in scientific methodology, and they often fail to fully comprehend the approaches employed by different forensic science disciplines and the reliability of forensic science evidence that is offered in trial. Such training is essential, because any checklist for the admissibility of scientific or technical testimony is imperfect. Conformance with items on a checklist can suggest that testimony is reliable, but it does not guarantee it. Better connections must be established and promoted between experts in the forensic science disciplines and law schools, legal scholars, and practitioners. The fruits of any advances in the forensic science disciplines should be transferred directly to legal scholars and practitioners (including civil litigators, prosecutors, and criminal defense counsel), federal, state, and local legislators, members of the judiciary, and law enforcement officials, so that appropriate adjustments can be made in criminal and civil laws and procedures, model jury instructions, law enforcement practices, litigation strategies, and judicial decision making.” 

Vincent Rust and Timothy Drewa, the Forensic Sciences Practice Group coordinators in our agency, are seeking to correct the deficits the NAS report identifies by promoting effective, creative advocacy in cases involving forensic science. Their work involves: 1) networking with lawyers and scientists throughout the country to learn of the available forensic resources and making that information available; 2) training staff; and 3) consulting on cases throughout the state.

To that end, the Forensic Sciences Practice Group coordinators, since their appointment in April 2012, have accomplished the following:

  • Met with top scientists and lawyers in the U.S. and Canada about creating an innovative forensic practice website that allows for an accessible and practical way to share resources and provide general guidance to staff attorneys and private bar attorneys who take Wisconsin State Public Defender's Office (SPD) appointments.
  • Developed training curriculum and materials to assist staff attorneys and the private bar with forensic issues.
  • Met with organizations, such as the Wisconsin Innocence Project, to find ways to work collaboratively, and at no added cost to the SPD, through grants, awards, etc., to train staff attorneys on sophisticated types of DNA testing and/or other forensic issues.
  • Assisted staff attorneys with Daubert challenges, cross examination of expert witnesses at trial, discovery demands, and finding qualified experts.

Vincent and Timothy look forward to continuing with these efforts and discovering how other public defense agencies approach the problem of defending cases involving forensic science and scientific experts.


For more information, please contact the Forensic Sciences Practice Group Coordinators:

To contact a Forensic Science Practice Coordinator (FPC), please download and complete the Forensic Team Assistance Request, which is linked below. Email the completed form to: This email address is being protected from spambots. You need JavaScript enabled to view it. and This email address is being protected from spambots. You need JavaScript enabled to view it.. We will assign your request to a FPC and the assigned FPC will contact you with 48 hours. 
Forensic Team Assistance Request Form

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Vincent Rust is an Assistant State Public Defender and Forensic Practice Coordinator at the SPD. As a Forensic Practice Coordinator, Vincent provides consultation and trial assistance to attorneys regarding forensic issues, coordinates agency interaction with forensic experts, works with the SPD Training Division in providing forensic training for attorneys and investigators, and helps maintain the SPD Forensics website. As an attorney and Asst. State Public Defender in LaCrosse County, Vincent represents clients in all types of criminal cases, from misdemeanor to intentional homicide cases, as well as Chapter 980 cases (Wisconsin's Sexually Violent Person Involuntary Commitment Law).  

Contact Vincent Rust: This email address is being protected from spambots. You need JavaScript enabled to view it.

Timothy Drewa
 is an Assistant State Public Defender in the West Bend Office. Timothy has represented clients in counties spanning from Vilas and Florence to Dane and Waukesha, appearing in approximately 17 counties in total. Timothy participated in the Wisconsin Innocence Project and Criminal Appeals project while at UW-Law School after he double majored in Corporate Finance and Operations Management. Timothy became a Forensic Practice Coordinator in October of 2019. His goal is to identify experts that are dedicated to professional diagnostic procedure to render valid opinions with the hopes of improving medical care and its impact on the justice system. Timothy has a working knowledge and interest in firearms and pediatric injuries.

Contact Timothy Drewa: This email address is being protected from spambots. You need JavaScript enabled to view it.