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Blood Breath & Tears XVISeptember 24-25, 2009
How to Deal With Blood Alcohol Evidence
Stefan Rose, M.D.
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AcknowledgementsHal SchuhmacherRichard Hersch
Kathryn Bradley
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Stefan Rose, M.D. e-mail [email protected]
University Medical and Forensic Consultants, Inc.10130 Northlake Boulevard Suite 214 - 300
West Palm Beach, Florida 33412
Phone (561) 795-4452 Fax (561) 795-4768
Toll Free 1-800-555-6449
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Stefan Rose, M.D.c.v. snapshot
Forensic PhysicianTrained in Forensic Toxicology and Psychiatry
First Director of the DUI Lab @ the University of MiamiPractice in Forensic Medicine and Courtesy Professor,
Department of Chemistry, FIU, Miami, FLResearch Projects include:
Forensic Reliability of Breath Alcohol TestingAlcohol Effects on Eyewitness Memory
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How to Deal With Blood Alcohol
Evidence
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Today’s Talk Blood
1.The Human Tissue 1.The Forensic Specimen
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Blood Alcohol Analysis1. Gas Chromatography
2. Enzyme Assay
Today’s Talk
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Interpretation of
Blood Alcohol Results
Today’s Talk
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Today’s Talk Summary of Errors in Blood Alcohol Testing
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Blood The Human Tissue
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http://www.nsbri.org/HumanPhysSpace/focus3/fig2.jpg
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Hemolysis
NORMAL
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Lipemia
NORMAL
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Jaundice
NORMAL
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Blood samples vary in composition from person to person, and vary in composition
within the same person depending on their condition (fasted, fed, hydrated, dehydrated, healthy, sick and so on)
These differences in blood composition may cause errors in the blood alcohol test
result depending on the test method.
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BloodThe Forensic Specimen
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Obtaining the Blood SampleN.I.K. Tri Tech
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N.I.K.
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Tri Tech
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Sodium Fluoride (NaFl) is a preservative, and is required to prevent
fermentation of the blood sample
No quality control procedures exist to detect fermentation in an FDLE
blood sample
100 mg of Sodium Fluoride is recommended as the minimum amount in a 10 ml tube of blood – some authors
recommend 200 mg
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1. The blood kit manufacturers do not make the blood tubes and therefore cannot prove the forensic reliability of the tubes
2. The State may lose their presumption if they cannot get direct testimony from the tube manufacturer
3. Incredibly, the wrong tubes with not enough sodium fluoride may have been used to collect the blood sample!
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Steps to Follow 1. Identify the Subject2. Inspect Blood Kit3. Apply Tourniquet4. Identify Blood Vessel5. Disinfect with Iodine6. Perform Venapuncture7. Remove Tourniquet8. Label and seal Tubes, Box9. Complete Paperwork
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An example of a properly sealed blood tube
Improperly sealed tubes
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Selecting a Blood Vessel
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Most Common Site For Blood Draw
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Trauma Blood Draws from the Femoral Artery
Most femoral blood draws are
arterial blood samples!
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What is wrong with this sample?
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Arterial blood may be up to 40% HIGHER in blood alcohol
concentration compared to venous blood!
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Blood Alcohol Errors So Far1. Non – compliance with Implied Consent2. Chain of custody errors3. Forensic Blood Collection Kit error4. Arterial instead of venous blood5. Contamination with fermenting microbes
Implied consent
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Blood Alcohol AnalysisGas Chromatography
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The analysis of any unknown sample includes:
1.Qualitative analysis2.Quantitative analysis
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Chromatography was first developed by the Russian botanist
Mikhail Tswett in 1903
Chromatography is a chemical technique that separates a complex mixture of compounds one
from another so that each compound may be analyzed individually without interference from
the other compounds in the mixture
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Regarding Blood Alcohol Analysis the complete designation for the chemical
technique is:
Static Headspace Gas Chromatography
with Flame Ionization Detection
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Most of us refer to it as
GC-FID
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Chromatographyis also known as Separation
Science
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Schematic Diagram of Gas Chromatography
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Complete GC-FID System44
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How Does the GC-FID Analysis Occur?
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Let’s start with the sample
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What Types of Test Samples may be analyzed?
1.Blank2.Negative Control3.Positive Control
4.Calibrator5.Unknown Sample
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What Types of Biologic Samples may be analyzed?
1.Blood2.Plasma3.Serum4.Urine
5.Ocular
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Blood sample is diluted0.10 ml blood1.0 ml water
Headspace sample taken for analysis
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Complete GC-FID System50
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Sample injectorFID detectors
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Schematic Diagram of Gas Chromatography
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Restek BAC Column
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What does the GC raw data look like?How is ethanol identified?
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1000
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Typical GC-FID Chromatogram
blank
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0
1000
2000
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injection peak
response
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Typical GC-FID Chromatogram
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2000
one compound
internal standardn-propanol
negative control
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response
injection peak
injection peak
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Typical GC-FID Chromatogram
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1000
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two compounds
internal standardn-propanol
ethanol
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response
injection peak
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Internal Standard
n-propanol
injection peak
ethanol
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injection peak
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What happens if two different compounds have the same retention time?
co-elution
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How is the co-elution error prevented with GC-FID analysis?
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Dual Column Analysis
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How is ethanol quantitatedwith GC-FID analysis?
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0.02 gram/dl
0.05 gram/dl
0.08 gram/dl
0.20 gram/dl
0.30 gram/dl
0.10 gram/dl
Ethanol Calibration Curveinstrument response
concentration
UNKNOWN SAMPLE ANALYZED
0.15
0.02 gram/dl
0.05 gram/dl
0.08 gram/dl
0.20 gram/dl
0.30 gram/dl
0.10 gram/dl
Ethanol Calibration Curve
instrument response
concentration
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Blood Alcohol Errors So Far1. Whole blood not used2. Negative control contaminated3. Sample mix-up in autosampler4. Fermentation in incubator5. Co-elution with single column GC6. Poor calibration curve
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Enzyme AssayAn enzyme is a special protein that speeds up a biochemical reaction
alcohol dehydrogenase
adh
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Ethanol enzyme assay measures NADH, NOT ethanol!!
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1. Hospital serum ethanol testing performed for medical, not legal purpose
2. No chain of custody – the sample results may belong to another patient
3. No sample available for independent re-test by opposing side
4. Serum ethanol result always higher than whole blood ethanol result
5. Hospital blood draw may obtain arterial blood instead of venous blood
Hospital Ethanol Enzyme Assay Test Errors
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1. Arterial blood may be 40% higher in ethanol concentration vs. venous blood
2. Hospital chemistry analyzers can cause false positive results
3. Hospital protocols do not follow forensic quality control guidelines
4. Hospital serum ethanol quantitative error is plus or minus 25%
5. Serum ethanol enzyme assay method prone to false positive results
Hospital Ethanol Enzyme Assay Test Errors
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Interpretation of
Blood Alcohol Results
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Typical Blood Alcohol Concentration Curve
BAC
Time (hours)
Blood sample @ 7:00 0.12 g/dl0.12
0.14
Predicted BAC @ 6:00 0.14 g/dl
absorption
peak
elimination
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What Does the Blood Alcohol Curve
Look Like in a Social Drinking Setting?
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The Assumptions Regarding Social Drinking and BAC’s at a Given
Point in Time by State’s Witness are Not Supported by the Evidence!
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Summary of Errors in Blood Alcohol Testing
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1. Non – compliance with Implied Consent2. Chain of custody errors3. Forensic Blood Collection Kit error4. Arterial instead of venous blood5. Contamination with fermenting microbes
Forensic
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1. Whole blood not used2. Negative control contaminated3. Sample mix-up in autosampler4. Fermentation in incubator5. Co-elution with single column GC6. Poor calibration curve
Forensic
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1. Hospital serum ethanol testing performed for medical, not legal purpose
2. No chain of custody – the sample results may belong to another patient
3. No sample available for independent re-test by opposing side
4. Serum ethanol result always higher than whole blood ethanol result
5. Hospital blood draw may obtain arterial blood instead of venous blood
Hospital Ethanol Enzyme Assay Test Errors
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1. Arterial blood may be 40% higher in ethanol concentration vs. venous blood
2. Hospital chemistry analyzers can cause false positive results
3. Hospital protocols do not follow forensic quality control guidelines
4. Hospital serum ethanol quantitative error is plus or minus 25%
5. Serum ethanol enzyme assay method prone to false positive results
Hospital Ethanol Enzyme Assay Test Errors
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Thank You!
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