L.A'S PREMIERE FORENSIC TOXICOLOGY EXPERT
expert witness
TOXICOLOGY EXPERT
Okorie Okorocha has two Master's Degrees in toxicology and pharmacology. Highly knowledgeable in the areas of Toxicology and Pharmacology, Okorie Okorocha has served as a drug and alcohol expert witness in over 140 trials, helping juries understand complex scientific concepts and ensuring that proper procedures are carried out in the case before the court.
more information. Forensic toxicology expert witness publication excerpt.
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This recent publication by Jaffe et al investigated an important and controversial topic—the association between blood alcohol concentration (BAC) and breath alcohol concentrations (BrAC) that are commonly used in law enforcement. The BAC/BrAC “partition ratio” is correction factor designed to optimally correlate BrAC (recorded as µg/L expired air) to true BAC (recorded as mg/dL blood). The BAC/BrAC ratio used in this study was 2100:1, which is accepted by the laws of Israel where the study was conducted, as well as in the United States. The authors indicate that their “study confirmed a high degree of correlation between BAC and BrAC.” This conclusion was based on the mean of all test results that were measured at several time points after alcoholic beverage consumption. While well-meaning, we believe that using the mean BAC/BrAC ratios to arrive at this conclusion is misleading and errantly interprets their data. The data in Figure 2 clearly indicate that significant overall variability existed between BrAC and BAC measurements obtained from any given individual, and this mismatch was oftentimes substantial. For the 181 comparisons that were made, the BAC/BrAC ratios ranged from 1214 to 2859 (rounded to integers). This range among individual measurements is profound, amounting to a 260% increase in BrAC-estimated BAC levels from the low-to-high calculated BAC/BrAC partition ratios.
In both the US an Israel, a driver with a BAC of 0.08% or higher (i.e. ≥80 mg/dL) is invariably subject to immediate arrest. A subject at the low end of the range with a 1214 ratio and a true BAC of 0.09%, who is by law a drunken driver, would have a purported BAC on the breath test of only 0.05% (0.052%, truncated to two decimal places without rounding, as is convention), making the driver appear to have a lower BAC than actually exists. Conversely, a legal driver with a BAC/BrAC ratio at the high end of the range (i.e., 2859) and a true BAC of 0.07%, would be arrested because he/she would produce an errantly calibrated BAC reading of 0.09%, which exceeds the legal limit. Thus, this great variability in true individual BAC to BrAC ratios continues to imprison innocent persons, while allowing another drunken driver to continue down the road.
The fact that a driver’s BrAC can vary by 260% is confounding to the authors’ conclusion that the “study confirmed a high degree of correlation between BAC and BrAC.” This conclusion is simply not supported by their data. Additionally, this large variability in individual BAC/BrAC ratios has already been published by Labianca and Simpson [1], which was not discussed by the authors.
Forensic Toxicology or Forensic Science issues, and forms the basis of for DUI Convictions
Okorie Okorocha, M.S., M.S., Forensic Toxicologist and Forensic Toxicology Expert Witness
The full paper published in the Albany Journal of Law and Technology.
Single Column Gas Chromatography is Proven to be Unreliable
“Dual column confirmation” is a process by which samples to be confirmed are run through a second gas chromatography (GC) in which the elution times of the compounds have been reordered. A dual column is necessary in order to confirm which of a number of compounds with similar retention times have been identified.” United States v. Atchison, Topeka & Santa Fe Ry. Co., CV-F-92-5068 OWW, 2003 WL 25518047 (E.D. Cal. July 15, 2003) affirmed in part, received in part sub nom. United States v. Burlington N. & Santa Fe Ry. Co., 520 F.3d 918 (9th Cir. 2008) received, 556 U.S. 599, 129 S. Ct. 1870, 173 L. Ed. 2d 812 (2009) and affirmed in part, received in part sub nom. United States v. Burlington N. & Santa Fe Ry. Co., 502 F.3d 781 (9th Cir. 2007) superseded on denial of reh’g en banc, 520 F.3d 918 (9th Cir. 2008) received, 556 U.S. 599, 129 S. Ct. 1870, 173 L. Ed. 2d 812 (2009) and affirmed in part, received in part sub nom. United States v. Burlington N. & Santa Fe Ry. Co., 479 F.3d 1113 opinion amended and superseded, 502 F.3d 781 (9th Cir. 2007) superseded on denial of reh’g en banc, 520 F.3d 918 (9th Cir. 2008) received, 556 U.S. 599, 129 S. Ct. 1870, 173 L. Ed. 2d 812 (2009).
Forensic Toxicology: The Fundamentals of Gas Chromatography (GC) for Blood Alcohol Analysis.
GC is the method used by California crime laboratories to test for alcohol (ethanol) in the blood of DUI suspects. The results are admitted into evidence at trial or presented to the defense to induce a plea bargain. GC is a form of chromatography (or separation) of a mixture of organic compounds. For the purpose of DUI prosecution, GC is used to separate the blood into the various individual volatile organic compounds (VOCs) that it contains. “Volatility” refers to the ease with which a chemical changes from the liquid state to the gaseous state. This is from where the “gas” in gas chromatography is derived. For example, the smell of alcohol on the breath is gaseous ethanol that has evaporated from the ingested liquid phase and exits through the lungs. After the compounds in blood have been separated, it is possible, with varying accuracy depending upon the method employed, to identify and quantify the amounts of the individual VOCs, including ethanol, present in a given sample. In GC testing, blood is warmed to vaporize the VOCs into a mixture of gasses. The VOCs in this vapor phase are then swept into and through a separation column using a stream of an inert gas (often helium). The column is a long, thin, heated, coiled tube (≈30 meters in length and ≤0.5 mm internal diameter is common for blood ethanol testing), with an inner lining composed of silica or various polymers that interact with VOCs to differing extents, depending on the VOC physical properties. Some VOCs bind very tightly to the column lining and take longer to pass through the column, while other VOCs bind very loosely and pass through quickly. Thus, the separated compounds in theory exit the column at different times, called “retention times” or “elution times.” Differing retention times are the result of the interaction of the blood VOC mixture with the column lining, column temperature, and selected carrier gas type and flow rate. The physical reactivity of the column lining to VOCs varies from column-to-column because of the use of different lining materials in different column types, and, within a single column type, because of non-uniformity in applying the lining during column production. Thus, each individual column requires rigorous standardization and calibration to ensure accurate functioning. As the compounds exit the column, they are typically detected using a Flame Ionization Detector (FID). The FID heats the eluted VOCs to their ignition temperature (i.e., they are burned) with a hydrogen/air flame. When organic compounds burn, their carbon molecules release cations (i.e., positively-charged ions) and electrons that form an electrical current that can be quantified when these particles pass between two electrodes in the detector. The current thus generated reflects the amount of a given compound and provides the results as the current produced (i.e., amount of chemical) at each retention time. This is analyzed by a computer and the results are presented as a graph of various peaks that correspond to different compounds.
Forensic Toxicology: Hospital serum blood tests versus Forensic Driving under the Influence (DUI)- whole blood tests, to be published in the Journal of Practical and Clinical Law.
Okorie Okorocha, M.S., M.S, J.D.
Hospital Blood Test Expert—Forensic Toxicologist.
The basics of Enzymatic Assay
An enzymatic assay method of blood ethanol testing is still used in both criminal DUI cases, and civil cases. This test is actually allowed as evidence in courts in the United States. This most flawed part of this test is that it does not have anything to do with the alcohol level but relies on an enzymatic reaction and the measurement of by-products. Various methods and techniques can be employed to measure the blood alcohol concentration. The most reliable and most used for legal purposes is Gas Chromatography used to determine BAC by Forensic Scientists and Forensic Toxicologists. Enzymatic assays, are quick and dirty screening tests and are always inaccurate due to a the margin of error inherent in the instrument (plus or minus < 25%), the enzyme assays tests serum samples, which are blood samples that have a significant non-alcohol portion removed, causing readings as falsely high as (plus or minus < 40%), false positives unknown sources introduce a margin of error (plus or minus < 100%), the difference between arterial blood which is usually used in emergency situation and venous blood which is the type of blood used in determining impairment introduces a margin of error (plus or minus < 40%), compounds that naturally occur in human blood samples [such a Lactate and Lactate Dehydrogenase] are falsely read as ethanol by the instrument introducing a margin of error (plus or minus < 100%), there are other random errors that have been discovered that occur with any of the above mechanisms and that introduces another margin of error (plus or minus < 100%).
[1] Okorie Okorocha, M.S. in Pharmaceutical Science with a Specialization in Forensic Science), M.S. in Forensic Toxicology, J.D., Forensic Lawyer, Pasadena, California.
In both the US an Israel, a driver with a BAC of 0.08% or higher (i.e. ≥80 mg/dL) is invariably subject to immediate arrest. A subject at the low end of the range with a 1214 ratio and a true BAC of 0.09%, who is by law a drunken driver, would have a purported BAC on the breath test of only 0.05% (0.052%, truncated to two decimal places without rounding, as is convention), making the driver appear to have a lower BAC than actually exists. Conversely, a legal driver with a BAC/BrAC ratio at the high end of the range (i.e., 2859) and a true BAC of 0.07%, would be arrested because he/she would produce an errantly calibrated BAC reading of 0.09%, which exceeds the legal limit. Thus, this great variability in true individual BAC to BrAC ratios continues to imprison innocent persons, while allowing another drunken driver to continue down the road.
The fact that a driver’s BrAC can vary by 260% is confounding to the authors’ conclusion that the “study confirmed a high degree of correlation between BAC and BrAC.” This conclusion is simply not supported by their data. Additionally, this large variability in individual BAC/BrAC ratios has already been published by Labianca and Simpson [1], which was not discussed by the authors.
Forensic Toxicology or Forensic Science issues, and forms the basis of for DUI Convictions
Okorie Okorocha, M.S., M.S., Forensic Toxicologist and Forensic Toxicology Expert Witness
The full paper published in the Albany Journal of Law and Technology.
Single Column Gas Chromatography is Proven to be Unreliable
“Dual column confirmation” is a process by which samples to be confirmed are run through a second gas chromatography (GC) in which the elution times of the compounds have been reordered. A dual column is necessary in order to confirm which of a number of compounds with similar retention times have been identified.” United States v. Atchison, Topeka & Santa Fe Ry. Co., CV-F-92-5068 OWW, 2003 WL 25518047 (E.D. Cal. July 15, 2003) affirmed in part, received in part sub nom. United States v. Burlington N. & Santa Fe Ry. Co., 520 F.3d 918 (9th Cir. 2008) received, 556 U.S. 599, 129 S. Ct. 1870, 173 L. Ed. 2d 812 (2009) and affirmed in part, received in part sub nom. United States v. Burlington N. & Santa Fe Ry. Co., 502 F.3d 781 (9th Cir. 2007) superseded on denial of reh’g en banc, 520 F.3d 918 (9th Cir. 2008) received, 556 U.S. 599, 129 S. Ct. 1870, 173 L. Ed. 2d 812 (2009) and affirmed in part, received in part sub nom. United States v. Burlington N. & Santa Fe Ry. Co., 479 F.3d 1113 opinion amended and superseded, 502 F.3d 781 (9th Cir. 2007) superseded on denial of reh’g en banc, 520 F.3d 918 (9th Cir. 2008) received, 556 U.S. 599, 129 S. Ct. 1870, 173 L. Ed. 2d 812 (2009).
Forensic Toxicology: The Fundamentals of Gas Chromatography (GC) for Blood Alcohol Analysis.
GC is the method used by California crime laboratories to test for alcohol (ethanol) in the blood of DUI suspects. The results are admitted into evidence at trial or presented to the defense to induce a plea bargain. GC is a form of chromatography (or separation) of a mixture of organic compounds. For the purpose of DUI prosecution, GC is used to separate the blood into the various individual volatile organic compounds (VOCs) that it contains. “Volatility” refers to the ease with which a chemical changes from the liquid state to the gaseous state. This is from where the “gas” in gas chromatography is derived. For example, the smell of alcohol on the breath is gaseous ethanol that has evaporated from the ingested liquid phase and exits through the lungs. After the compounds in blood have been separated, it is possible, with varying accuracy depending upon the method employed, to identify and quantify the amounts of the individual VOCs, including ethanol, present in a given sample. In GC testing, blood is warmed to vaporize the VOCs into a mixture of gasses. The VOCs in this vapor phase are then swept into and through a separation column using a stream of an inert gas (often helium). The column is a long, thin, heated, coiled tube (≈30 meters in length and ≤0.5 mm internal diameter is common for blood ethanol testing), with an inner lining composed of silica or various polymers that interact with VOCs to differing extents, depending on the VOC physical properties. Some VOCs bind very tightly to the column lining and take longer to pass through the column, while other VOCs bind very loosely and pass through quickly. Thus, the separated compounds in theory exit the column at different times, called “retention times” or “elution times.” Differing retention times are the result of the interaction of the blood VOC mixture with the column lining, column temperature, and selected carrier gas type and flow rate. The physical reactivity of the column lining to VOCs varies from column-to-column because of the use of different lining materials in different column types, and, within a single column type, because of non-uniformity in applying the lining during column production. Thus, each individual column requires rigorous standardization and calibration to ensure accurate functioning. As the compounds exit the column, they are typically detected using a Flame Ionization Detector (FID). The FID heats the eluted VOCs to their ignition temperature (i.e., they are burned) with a hydrogen/air flame. When organic compounds burn, their carbon molecules release cations (i.e., positively-charged ions) and electrons that form an electrical current that can be quantified when these particles pass between two electrodes in the detector. The current thus generated reflects the amount of a given compound and provides the results as the current produced (i.e., amount of chemical) at each retention time. This is analyzed by a computer and the results are presented as a graph of various peaks that correspond to different compounds.
Forensic Toxicology: Hospital serum blood tests versus Forensic Driving under the Influence (DUI)- whole blood tests, to be published in the Journal of Practical and Clinical Law.
Okorie Okorocha, M.S., M.S, J.D.
Hospital Blood Test Expert—Forensic Toxicologist.
The basics of Enzymatic Assay
An enzymatic assay method of blood ethanol testing is still used in both criminal DUI cases, and civil cases. This test is actually allowed as evidence in courts in the United States. This most flawed part of this test is that it does not have anything to do with the alcohol level but relies on an enzymatic reaction and the measurement of by-products. Various methods and techniques can be employed to measure the blood alcohol concentration. The most reliable and most used for legal purposes is Gas Chromatography used to determine BAC by Forensic Scientists and Forensic Toxicologists. Enzymatic assays, are quick and dirty screening tests and are always inaccurate due to a the margin of error inherent in the instrument (plus or minus < 25%), the enzyme assays tests serum samples, which are blood samples that have a significant non-alcohol portion removed, causing readings as falsely high as (plus or minus < 40%), false positives unknown sources introduce a margin of error (plus or minus < 100%), the difference between arterial blood which is usually used in emergency situation and venous blood which is the type of blood used in determining impairment introduces a margin of error (plus or minus < 40%), compounds that naturally occur in human blood samples [such a Lactate and Lactate Dehydrogenase] are falsely read as ethanol by the instrument introducing a margin of error (plus or minus < 100%), there are other random errors that have been discovered that occur with any of the above mechanisms and that introduces another margin of error (plus or minus < 100%).
[1] Okorie Okorocha, M.S. in Pharmaceutical Science with a Specialization in Forensic Science), M.S. in Forensic Toxicology, J.D., Forensic Lawyer, Pasadena, California.
