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Drug Testing Advisory Board Biographical Information


DTAB Members Biographies


Carl Christensen, M.D., MI

Carl Christensen, M.D. has been certified as a Medical Review Officer (MRO) since 2005; he currently works as an MRO reviewing DOT, non-DOT and healthcare professional drug testing results for Vault Workforce. He has just been appointed to the MROCC Exam Development Committee. He has been an addiction provider for the Michigan’s Physician Monitoring Program (the Michigan Health Professional Recovery Program) since 2009; the Chair of the oversight committee until 2013; and the current Medical Director since 2014. He serves as an expert witness for the DEA and the US Attorney’s Office and local law enforcement and develops Continuing Medical Education for the Michigan State Medical Society in pain and addiction management. Dr. Christensen is also a Clinical Associate Professor of Psychiatry and Obstetrics and Gynecology at the Wayne State University (WSU) School of Medicine in Detroit. While an Associate Professor, he served as the Medical Director for the Substance Abuse Research Division at WSU; the Medical Director of the Eleonore Hutzel Recovery Center, specializing in the treatment of pregnant addicted women; the Associate Residency Director and Medical Clerkship Director in the Department of OB Gyn at the Detroit Medical Center. He is Board Certified in addiction medicine and obstetrics and gynecology and a Distinguished Fellow of the American Society of Addiction Medicine.

David A. Engelhart, Ph.D., D-ABFT-FD, OH

Dr. Engelhart has served as the Laboratory Director for Omega Laboratories, Inc. since 2005 and has over 26 years of experience in forensic toxicology. Omega Laboratories, Inc. is a forensic drug testing facility located in Mogadore Ohio which focuses on the analysis of hair and oral fluid specimens for drug of abuse. His prior employment was with the Office of the Cuyahoga County Coroner located in Cleveland Ohio where he was instrumental in the toxicology laboratory acquiring and maintaining ABFT accreditation.

David received his Bachelor of Science degree in Chemistry from Hiram College and his Doctorate Degree in Chemistry from Case Western Reserve University. He is a board-certified Diplomate of the American Board of Forensic Toxicology in Forensic Drug Toxicology and an inspector for the College of American Pathologists Forensic Drug Testing laboratory accreditation program and a member of the Society of Forensic Toxicologists.

E. Lindsey Everson, J.D., TX

Lindsey Everson is a partner with Caldwell Everson P.L.L.C. Mr. Everson has represented some of the largest forensic drug testing laboratories in the United States. He has also provided legal services to third-party administrators and medical review officers in litigation nationwide. Besides providing laboratories and third-party administrators legal services across the country, he also provides consultation and litigation services to other workplace drug testing entities, including employers and collection sites. Lindsey has consulted with both non-certified laboratories and SAMHSA-certified laboratories regarding compliance with National Laboratory Certification Program guidelines and FDT industry standards for forensic workplace drug testing. On behalf of various drug-testing industry entities, he has offered his expertise to Firm clients providing documentary and testimonial evidence in Department of Transportation enforcement proceedings. Lindsey also provides services to Firm clients in proceedings and investigations brought by federal and state agencies with regulatory oversight authority over various FDT entities. Lindsey regularly represents and provides legal advice to Firm clients regarding third-party requests for federal and state-regulated drug testing information and records.

Lindsey received his Bachelor of Arts Degree in Political Science in May 1994 at Texas A&M University and his Juris Doctorate, Cum Laude from the University of Houston Law Center in May 1997 following which he was admitted into the Bar in the U.S. District Court, Eastern, Northern and Southern Districts of Texas.

Michael Grommes, D-ABFT-FD, AZ

Michael Grommes has been a Forensic Toxicologist for 28 years. He is a 1994 graduate of Arizona State University with a B.S. in Chemistry. In 2006, he also completed the Degreed Certificate Program in Forensic Toxicology from the University of Florida. Mike is a full member of the Society of Forensic Toxicologists (SOFT), a member of the California Association of Toxicologists (CAT) and a Diplomate of the American Board of Forensic Toxicology (D-ABFT-FD). He has been certified by the Arizona Department of Public Safety as an Arizona Licensed Alcohol Analyst since 1994 . Michael has also been an NLCP Federal Laboratory Inspector since 2013. He is the toxicologist for Blood Alcohol Testing & Consulting, LLC since 1999 and is the Laboratory Director/RP and co-owner of Desert Tox, LLC, Arizona’s only SAMSHA/HHS/DOT certified laboratory, which opened in 2017. He has testified in hundreds of cases in various courts throughout the State of Arizona on drug and alcohol related cases. He has also been an Adjunct Professor of Forensic Toxicology at Arizona State University since January 2022.

Dawn M. Hahn, M.B.A., M.T. (ASCP), D-ABFT, KS

Dawn Hahn is the Lab Operations Director and Responsible Person of the Quest Diagnostics Employer Solutions Laboratory in Lenexa, Kansas. Dawn obtained her Bachelor of Arts degree in medical technology from Northwestern College and obtained her M.B.A. from JHU. Prior to joining Quest Diagnostics, Dawn worked as a medical technologist in several clinical laboratories. She joined Home Office Reference Laboratory (HORL) in 1987 performing risk assessment testing for life insurance applicants. HORL eventually became LabONE, which then became Quest Diagnostics in 2005. LabOne obtained its SAMHSA certification in 1994. Dawn played a significant role in the lab obtaining this certification. She has worked for Quest Diagnostics for over 35 years and has held several different roles in the SAMHSA certified laboratory. In her current role, which she has held for over 9 years, she oversees one of the largest workplace drug testing labs in the nation. Quest Diagnostics performs drug testing in urine, oral fluid and hair so Dawn will bring much experience and knowledge to the board as we add alternate matrices to the Federal Program. Dawn has been a consultant for the National Laboratory Certification Program since 2005 performing inspections and serving on the oral fluid lab manual working group. Dawn is a board-certified Diplomate with the American Board of Forensic Toxicology (ABFT) and a member of the Society of Forensic Toxicologists.

David K. Roberts, Ph.D., F-ABFT, OR

Dr. David Roberts is a private toxicology consultant with Cascade Toxicology and prior Manager and Responsible Person for Legacy Health, Legacy Laboratory Services in Portland, Oregon, a laboratory certified by the Substance Abuse and Mental Health Services Administration to perform drug testing for specimens regulated by the Federal Workplace Drug Testing Program. He directed the College of American Pathologist Forensic Drug testing as well as the Forensic Specimen Collections services that perform DOT regulated evidential breath alcohol testing.

David earned his Bachelor of Arts degrees in Chemistry and Biology at the University of Missouri at Kansas City and his Ph.D. in Toxicology from Texas A&M University. David is a board-certified Fellow with the American Board of Forensic Toxicology (ABFT) and a member of the Society of Forensic Toxicologists, the American Chemical Society and the Association for Diagnostics and Laboratory Medicine. David is an inspector for the College of American Pathologists Forensic Drug Testing laboratory accreditation program as well as the National Laboratory Certification Program.

Bryan Ruggery, MFS, D-ABFT-FT, VA

Mr. Ruggery presently serves as a Drug Science Specialist with the Drug and Chemical Evaluation Section in the Diversion Control Division of the Drug Enforcement Administration. His responsibilities include providing leadership on technical and scientific matters associated with drugs and toxicology while assisting with drug control scheduling actions, processing exemption applications, evaluating control status inquiries, and analyzing data from the National Forensic Laboratory Information System (NFLIS). He also participates in scientific conferences and inter- and intra- agency meetings concerning drug issues and chemical control. Bryan earned a Bachelor of Science in Applied Forensic Sciences from Mercyhurst College in 2007 and a Master of Forensic Science in Forensic Toxicology from The George Washington University in 2009. He has formerly held several relevant positions. He served as a Medical Technologist at Quest Diagnostics Nichols Institute in Chantilly, VA. He also served as a Forensic Toxicologist with the Office of the Chief Medical Examiner (OCME) in Washington, DC., where he conducted toxicological and drug analysis on Medicolegal Death Investigation, Driving Under the Influence, and Drug Facilitated Crime related casework.

Bryan earned board-certification as a Diplomate with the American Board of Forensic Toxicology (ABFT) and is a full member of the Society of Forensic Toxicologists (SOFT) and an associate member in the Toxicology Section of the American Academy of Forensic Sciences (AAFS).

Alison Stockdale, VA

Alison Stockdale is the Branch Chief/Drug Program Manager with the Department of the Interior, ensuring proper execution of the Department’s Drug-Free Workplace Program. Additionally, as part of the Interior Business Center, her office provides support services to 70 other federal agencies assisting in the execution of their Drug-Free Workplace programs. Her staff assist customers with random testing selection, scheduling, testing, applicant notification, training and on-site collection services. Ms. Stockdale is the Contracting Officer’s Representative for two contracts which are responsible for 50,000 drug tests annually. She is a trained collector and has performed thousands of urine collections. She is a subject matter expert in Federal Workplace Drug Testing policy.

Alison received her Bachelor Degree in Government from Sweet Briar College and a Master Certificate in Business Skills from George Washington University School of Business.

Elizabeth “Libby” B. Stuyt, M.D., CO

Dr. Stuyt is a board-certified Addiction Psychiatrist who has worked in the addiction/behavioral health field since 1990 and was the Medical Director for the Circle Program, a 90-day inpatient treatment program. She works currently as a consultant for Solvista Behavioral Health in Salida, Colorado and educates people nationally on the effects of high potency THC on the developing brain. She is recognized as an expert in interpreting drug test results. Her knowledge of addiction psychiatry and THC is a beneficial addition to DTAB.

Libby earned her Bachelor of Science degree in Biomedicine and a Master of Science degree in Biochemistry from Texas A&M University, and her Doctor of Medicine degree from Texas Tech University.

Samantha S. Tolliver, Ph.D., Washington DC

Samantha S. Tolliver, Ph.D., is the Chief Toxicologist at the Washington, DC Office of the Chief Medical Examiner and has been employed there since 2014. Her eighteen years of toxicology experience include postmortem, driving under the influence, drug facilitated crime, pre/post-exposure, and workplace drug testing. Her testimony experience encompasses civil (family law) and criminal cases within the States of Texas, Massachusetts, and the District of Columbia. Dr. Tolliver holds a Bachelor of Science in Chemistry from West Virginia State University. She earned both her Master of Science in Forensic Science and a Doctorate in Chemistry from Florida International University. She is certified in toxicology by the National Registry of Certified Chemists. Dr. Tolliver has made scientific presentations at the Drug & Alcohol Testing Industry Association, the American Academy of Forensic Scientists, and the Society of Forensic Toxicologists (SOFT). Dr. Tolliver is an active member of SOFT, and the American Academy of Forensic Sciences.

Last Updated

Last Updated: 04/24/2023

Last Updated