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?