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How do the police test for alcohol in a blood sample?

How do the police test for alcohol in a blood sample?

Keep in mind that a police-administered blood test creates an estimate of the amount of alcohol that is in a blood sample. Like all estimates, it can be accurate or inaccurate, depending upon the circumstance. The police crime labs use head-space gas chromatography with a flame ionization detector to analyze blood samples. It is a very well-respected and reliable method of testing blood for alcohol, but the people who work in the crime labs often have minimal education, poor training, inadequate facilities and unscientific laboratory protocols.

Blood is collected by a phlebotomist in two grey-top tubes which should contain a preservative and anticoagulant (grey-top tubes are normally used in medicine for glucose-testing). One tube is for the crime lab to test and the other is preserved for the subject’s independent testing purposes.

At the crime lab, one tube is opened and the contents are poured into a clean container. A measured amount of blood and a type of alcohol (usually n-propanol) are mixed together into a head-space vial, which is then crimp-sealed. The vial is placed into a rack called an auto-sampler with up to 123 other vials. Each vial is heated and rocked to allow volatile compounds to rise into the head-space above the liquid in the vial. When equilibrium of the ratio of volatile compounds in the liquid to the volatile compounds in the head-space is reached, the head-space gas is sampled.

A syringe pierces the crimp-seal and another gas (generally helium) is used to force the head-space gas out of the vial and into a hot injector port of a machine called a “gas chromatograph” (GC).

The head-space gas travels through a capillary column which is about 30 meters long and nearly as thin as a human hair. By chemical and mechanical means, the molecules traveling through the column are slowed down to different speeds, depending on the type of molecule. They elute (exit) the column at predictable times and are burned by a flame. The burning of the molecules creates ion energy which is measured by a flame ionization detector and converted by a computer formula to a blood alcohol estimate.

Head-space gas chromatography is a “separation science” and relies on the ability of the process to separate out various compounds and measure quantities so small that they cannot be seen with the human eye. Small mistakes in preparation of the sample will lead to large mistakes in the results.

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James Nesci

James Nesci

James Nesci often defends cases well into the .30 blood-alcohol range. He has caught more than one police officer lying during cross-examination and some police officers have even refused to grant pretrial interviews to him without a prosecutor or their own counsel present. He was one of the lead attorneys on the Intoximeters® RBT-IV breath-testing issue in Southern Arizona which resulted in the suppression of breath tests in over 7,000 cases and the removal of the RBT-IV from the streets of Arizona. He also spear-headed the effort to obtain the manufacturer’s source code and software for the CMI Intoxilyzer 8000. Although the source code was never obtained, he almost single-handedly ground 90% of all DUI prosecutions within the City of Tucson to a halt for nearly three years and obtained breath test suppressions and dismissals in hundreds of DUI cases. In addition to “traditional” DUI cases which involve alcohol, Mr. Nesci is a recognized expert on the defense of DUI/Drugs cases. Whether they be legal-over-the-counter-medications, prescription medications or illicit drugs, such DUI cases are far more complex and present cutting-edge issues for the courts. He is qualified to administer Standardized Field Sobriety Tests under National Highway Traffic Safety Administration & International Association of Chiefs of Police Guidelines. In 2006, he was appointed Regent of the National College for DUI Defense, Inc. He was formerly the chair of the Curriculum Committee for the NCDD. Currently, he is the State Delegate Coordinator, a member of the Amicus Committee, Treasurer of the NCDD, Member of the Executive Committee and served as an oral argument judge for the Board Certification Committee. Mr. Nesci is the author of Arizona DUI Defense: The Law & Practice, a legal treatise written for DUI defense attorneys and published by Lawyers and Judges Publishing Company (now in its third edition) [www.lawyersandjudges.com]. In 1999 Mr. Nesci became a Sustaining Member of the National College for DUI Defense [www.NCDD.com]. In 2001, he was Board Certified by the National College for DUI Defense, Inc., which is a is recognized by the American Bar Association. He is one of only three Board Certified attorneys in the State of Arizona, and one of less than fifty Board Certified attorneys in the nation (as of January, 2012). Mr. Nesci has lectured from coast-to-coast for such organizations as The University of Arizona James E. Rogers College of Law, Arizona State University College of Law Alumni Association, University of Mississippi CLE Department, South Texas College of Law CLE Department, Arkansas Association of Criminal Defense Lawyers, Arizona Attorneys for Criminal Justice, Arizona Public Defenders Association, California Attorneys for Criminal Justice, City of Phoenix Public Defender's Office, Colorado Criminal Defense Bar, Florida Association of Criminal Defense Lawyers, Indiana Public Defender’s Council, Kansas Association of Criminal Defense Lawyers, Louisiana Association of Criminal Defense Lawyers, Maricopa County Bar Association, Maricopa County Public Defender's Office, Maryland Criminal Defense Attorneys Association, the Mexican-American Bar Association at Loyola, the National Association of Criminal Defense Lawyers, the National College for DUI Defense, the Nebraska Criminal Defense Attorney’s Association, the Nevada State Bar Association, the New York State Bar Association, the Ohio Association of Criminal Defense Lawyers, the Pima County Bar Association, the Pima County Bar Association Young Lawyer’s Division, the Texas Criminal Defense Lawyers Association, the Tucson City Public Defender’s Office, the Tulare County (California) Public Defender’s Association, the Utah Criminal Defense Lawyers Association, and the Washington Foundation for Criminal Justice. He has taught seminars on the subjects of Ethics, 4th Amendment Law, Drug Recognition Evaluations (DUI-Drugs/DRE), Cross-Examination, Trial Tactics, Jury Selection, Field Sobriety Testing, Driving Behavior, Blood Alcohol Calculations, Opening & Closing Arguments, Source Code Litigation, Frye & Daubert Challenges, Intoxilyzer 8000 Operator’s Course, Headspace Gas Chromatography, Blood and Breath Testing. He has represented former Supremes lead singer Diana Ross and Tampa Bay Buccaneers' Tight-End Jerramy Stevens on Extreme DUI charges and fitness guru Richard Simmons on an assault charge. Mr. Nesci lives in Tucson with his wife and twin daughters. He is an honorably discharged veteran of the U.S. Navy where he spent much of his time working as an electrician in the Philadelphia Naval Shipyards. His interests are traveling, fine wines, vintage port and fast cars. He is an amateur race car driver, an accomplished mechanic, and a Corvette fanatic.

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