See also: John Bederka Civil Trial Testimony

Report of John Bederka, Ph.D.

From the Report January 29, 1998

Materials Evaluated:

1. Investigating officer's report of motor vehicle accident;

2. Official report of the Iowa Department of Public Safety, DCI Laboratory;

3. The Department of Transportation request for specimen;

4. A copy of Tracy Rokes; driver's license reflecting his date of birth and weight;

5. Statement of Sgt. Wilson with the Cedar Falls Police Department of Tracy Rokes on 10/05/96

6. Sartori Memorial Hospital laboratory report reflecting results of the legal blood alcohol level;

7. Blood collection report;

8. Statement taken by Officer Robert B. Anderson with the Cedar Falls Police Department of Ronnie Rose Young on 10/07/96 reflecting the time Defendant Tracy Rokes left Brewsters;

9. Statement taken by Officer Robert B. Anderson of Craig Allan Young on 10/07/96 which reflects the time Tracy Rokes arrived and left Brewsters;

10. Narrative report by Officer Robert B. Anderson dated 10/07/96 stating information concerning informing Tracy Rokes of the results of his blood test;

11. Narrative report dated 10/04/96 by Officer Robert B. Anderson which contains information concerning testing of Rokes;

12. Narrative report by Officer Robert J. Michael dated 10/05/96 including information about the withdrawal of blood from T. Rokes;

13. Ambulance sheet concerning Tracy Rokes dated 10/04/96;

14. Transcripts in the matter of State of Iowa v. Tracy Rokes (Volumes I through V);

15. See copies of the Title pages of the 12 Articles (enclosed under separate cover).

Presumed Facts:

1. The accident in question occurred at about 22:50 hours on October 4, 1996.

2. Alcohol consumption in the form of Been by Mr. Rokes occurred during about 2.5 hours from about 20:00-23:00 hours on October 4, 1996.

3. As per Mr. Rokes' statements, he consumed about 6 Beers during about 2.5 hours of drinking with 3 Beers having been consumed during the last 1 hour before his leaving the establishment knows as Celebrations.

4. The scientific evidence literature notes that after the consumption of 6 Beers in one hour, the Blood Alcohol Concentration (BAC) peaks within 10 minuets after the cessation of drinking. Whereas, after the consumption of about 8-10 Beers in about 2 hours, the BAC peaks within about 25 minutes after the cessation of drinking. Studies that report longer times to peak BAC were carried out with the ingestion of whiskey and/or simulated whiskeys usually consumed with a periods of about 15 minutes.

5. The rate of decline of the BAC after Beer drinking, in reference to Item 4, immediately above, was between .0014 and .0029% per hour. Trauma victims are reported to have a more rapid rate of decline of BAC.

6. The conversion of a Plasma "BAC" to a Whole Blood-Equivalent BAC will be most likely within the factor of 1.10 to 1.17 irrespective of hematocrit.

7. The analytical precision and accuracy of the Alcohol analyses at Sartori and DCI were equally proficient in terms of results as shown and as stated.

8. Diverse observation of Mr. Rokes, as noted in the File Materials, such as Wobbly, Stumbling, Staggering, Odor of Alcohol on the Breath and Face Flushed, allow that Mr. Rokes was "Frankly Intoxicated".

9. The value of 120 mg/dl reported by Sartori Memorial Hospital Laboratory was the concentration of Ethyl Alcohol (alcohol ) in a plasma specimen obtained from Mr. Rokes at 00:28 on October 5, 1996. The result of 0.087 grams of alcohol in 100 ml of Whole Blood was obtained by headspace gas chromatography on an apparently duplicate specimen which was drawn on 10/05/96. However, the exact conditions of storage, transfer, and, preparation/analysis during the 25 days until October 30, 1996 allow that this specimen had deteriorated, as per Mr. Rayburn's statement.

Results of the BAC Calculations:

The Plasma Alcohol Value of 120 mg/dl (0.125%) when corrected for the conversion to a Whole Blood Equivalent value affords a range of 103-109 mg/dl (0.103-0.109%) at the drawing time of 00:28 on October 5, 1996. Thus, the BAC Profile of Mr. Rokes back to the time of the accident is probably as follows:

BAC Range (%)

Date Time 0.014% per hr. 0.020% per hr.



0.014% per hr.

0.020% per hr.



0.103 - 0.109

0.103 - 0.109



0.117 - 0.123

0.132 - 0.138



0.124 - 0.130

0.147 - 0.153


From the foregoing, it can be concluded/opined that the BAC of Mr. Rokes at about the time of the accident in question was most probably between 125 and 155 mg/gl (0.125 and 0.155%). Furthermore, at this BAC, Mr. Rokes would have greater than a 50% Probability of being adjudges as "Frankly Intoxicated". Among the psychomotor functions that would be adversely affected at BAC's above 0.125% are the following:

Peripheral Vision During Multitasking
Color Discrimination
Depth Perception
Clear Headedness
Short-term Memory

Respectfully submitted,

John P. Bederka, Jr., Ph.D.
Consulting Toxicologist


Documents used by Dr. Bederka:

Bederka, John, Jr.; "Drugs in sports: testing and considerations on performance enhancement", JOURNAL OF PHARMACY PRACTICE (1996), 9 (5): 379-385..

Bederka, John, Jr.; "Lead 'poisoning' and pharmacotherapy: is the cure necessary, and worse than the 'disease"?, JOURNAL OF PHARMACY PRACTICE (1995), 8 (5): 245-258.

Crow, K. E. Batt, R. E., (Eds.); Human metabolism of alcohol, volume I: Pharmacokinetics, medicolegal aspects and general interest; CRC Press (1989), 214p.

Goldberg, Leonard; "Quantitative studies on alcohol tolerance in man", ACTA PHYSIOLOGIC SCANDINAVIA (1943), 5 (Supplement XVI): 7-128.

Gordon, I, et al; "Medico-legal aspects of acute alcoholic intoxication" . . .In: FORENSIC MEDICINE (1988) 15: 396-435.

Gustafson, R.; Kallman, H.; "The Blood alcohol curve as a function of time and type of beverage: methodological considerations," DRUGS AND ALCOHOL DEPENDENCE (1988), 21: 243-246. (Breath alcohol.)

Janus, J. T.; Shajani, N. K.; Image, B. A.; "Consumption of a large dose of alcohol in a short time span", FORENSIC SCIENCE INTERNATIONAL (1992): 56: 113-125. (16 subjects in 30 minutes, breath alcohol test)

Jones, A. W.; "Disappearance rate of ethanol from the blood of human subjects: implications for forensic toxicology," JOURNAL OF FORENSIC SCIENCES (1993), 38 (1) : 104-118.

Prouty, Richard W., Anderson, William H.; "A comparison of postmortem heart blood and femoral blood ethyl alcohol concentrations", JOURNAL OF ANALYTICAL TOXICOLOGY(1987): 11: 191-197.

Roine, Risto P.; Gentry, Thomas; Lim, Robert T., Jr.; Helkkonen, Erikki; Salaspuro, Mikko; Lieber, Charles S.; "Comparison of blood alcohol concentrations after beer and whiskey", ALCOHOLISM: CLINICAL AND EXPERIMENTAL RESEARCH (1993), 17 (3): 709-11

"Stages of acute Alcoholic Influence/ Intoxication in Nontolerant Individuals" in Matthew J. Ellenhorn, Donald G. Barcelous, MEDICAL TOXICOLOGY: DIAGNOSIS AND TREATMENT OF HUMAN POISING,, Elsevier, p793. based on the chart found in Dubowski, K.; "Method for alcohol determination in biological liquids by sensing with a solid-state detector," CLINICAL CHEMISTRY (1976) 22 (6), p863-67.

Widmark, E. M. P., "PRINCIPLES AND APPLICATIONS OF MEDICOLEGAL ALCOHOL DETERMINATION", 1932 (1981), Urban & Schwarzenberg, 1932, pp. 110-137p.

Winek, C. L.; Carfagna, M.; "Comparisons of plasma, serum, and whole blood ethanol concentrations," JOURNAL OF ANALYTICAL TOXICOLOGY (1987), 11: 267-68.

Zink, P.; Reinhardt, G.; "Course of the blood alcohol-curve during and after consumption of alcohol in large amounts", BLUTALKOHOL (1984), 21: 422-442.

Zink, P.; Reinhardt, G.; "Course of the blood alcohol-curve during and after consumption of alcohol in large quantities: long time studies on human volunteers. . .In: K. Kuriyama; A. Takada; H Ishii (Eds.) Biomedical and social aspects of alcohol and alcoholism, Amsterdam, The Netherlands: Elsevier Science Publishers B. V., 1988, 892p. (p.623-628).  


Supplements to the report March 25, 1999

I am herewith affording a supplemental report relative to the above-mentioned Matter; This report deasl with three topical areas:

1. I recently afforded your Office a copy of an article by Prouty and Anderson. A conclusion from the data is that certain whole blood samples that were maintained in Sodium Fluoride containing tubes afforded Blood Alcohol Analysis results that were about 10-20% less than the values obtained on the earlier initial analysis of the samples. IF one applied this correction to the Rayburn analysis in this Matter, then the corrected range of his Whole Blood Results would be about 0.098-0.107%. This Range is quite similar to the proposed values of 0.103-0.109%, as per my report of January 29, 1998.

2. I am affording your Office a copy of a recent article that addresses the topic of "estimation of blood alcohol concentrations after social drinking" which was coauthored by Stowell and Stowell. This article validates the process of using ranges of rates of alcohol metabolism (dissipation) by the body in attempts to extrapolate from single measurements of Blood Alcohol Concentrations at tomes post-drinking also per my letter of January 29, 1998..

3. Using the information in the File for Mr. Roses and the table in the text by Crow and Batt on page 54, it can be shown that Mr. Rokes had about 6 beer-equivalents of alcohol present in his body at the time of the blood sampling. Given that he had been drinking for about 4.5 hours prior to the blood sampling, his body would have eliminated about 3 beer-equivalents of alcohol during that time. This during the evening, Mr. Rokes would have to have consumed about 9 beers rather than the 6 listed in his reports.

updated 12/12/16