Pesticides and Insecticides Contaminants Expert Witnesses: 4

Paul E. Rosenfeld, M.S., Ph.D., is the Founder and Principal Scientist of RoseyFields LLC and a nationally recognized forensic environmental scientist and plaintiff expert witness. Over 25 years, his work has spanned complex toxic-tort and class-action litigation — including MTBE, PFOA/PFAS, asbestos, FELA railroad exposure, air-dispersion modeling, epidemiology, toxicology, industrial contamination, and pesticide exposure matters — with an aggregate case value of approximately $14 billion, and he has been deposed approximately 150 times in 31 states.

Litigation Support

Dr. Rosenfeld's opinions are based on established scientific methodologies, quantitative exposure models, peer-reviewed scientific literature, published technical methods, and reproducible calculations that can be independently evaluated and tested, providing a rigorous scientific foundation for expert opinions under Daubert and related standards for the admissibility of scientific evidence. He has authored and contributed to books and technical publications concerning environmental contamination, exposure assessment, and risk evaluation and has applied these scientific methods in expert reports, litigation, depositions, regulatory proceedings, and trial testimony.

Methodologies & Scientific Approach

Dr. Rosenfeld's air dispersion modeling work applies EPA-approved and peer-reviewed models, including AERMOD, CALPUFF, and ALOHA, to reconstruct historical emissions, source attribution, and community-level exposure pathways. His exposure and dose reconstruction methods integrate environmental sampling data, regulatory exposure factors, and published toxicological and epidemiological literature to quantify human exposure to chemicals including benzene, PFAS/PFOA, TCE, hexavalent chromium, and crystalline silica, among others. Each methodology is applied transparently, allowing the underlying calculations, data inputs, and modeling assumptions to support general cuasation opinions. 

Publications & Court Qualifications

Dr. Rosenfeld has authored six books and dozens of peer-reviewed publications on environmental contamination and risk assessment. He has been qualified as an expert under Daubert and analogous standards in federal and state courts nationwide reflecting consistent application of scientifically defensible methodologies under prevailing standards for expert testimony admissibility.

Areas of Expertise:

Rudolph Johnson, PhD, is a Chemical Toxicologist with over 20 years of experience in analytical chemistry and toxicological investigations. Dr. Johnson's past experience includes directing the (1) clinical toxicology network, LRN-C, at the Centers for Disease Control and Prevention and (2) the Military Exposures Research Program at the US Department of Veterans Affairs. Currently, he serves as the Director of the Wisconsin State Laboratory of Hygiene and has a faculty appointment at the University of Wisconsin-Madison School of Medicine and Public Health, Department of Pathology.

Dr. Johnson focuses on two specialty areas:

(A) Toxicology: He offers causation opinions connecting dose, analytical detection, and biomarker findings to determine whether and to what extent an individual was exposed to a chemical or toxin.  The chemical or toxin may be inhaled, ingested or injected. This includes drug and alcohol testing.

(B) Laboratory Testing: He critiques or defends laboratory testing methodology, chain-of-custody, and quality assurance practices. He is an expert at evaluating conflicting testing data between two labs.

Litigation Support - Dr. Johnson works with plaintiff and defense litigation attorneys on toxic tort, product liability, and environmental and occupational exposure cases requiring causation analysis. He supports criminal defense and plaintiffs reviewing drug exposures (opioids, fentanyl analogs, polypharmacy) and alcohol testing. This includes chain-of-custody, and quality practices. Conflicting or inconsistent laboratory data, especially between multiple laboratories, is a specialty area of Dr. Johnson because he previously directed multiple clinical toxicology labs.

Dr. Johnson detects, quantifies, and interprets chemical and toxic exposure in human clinical samples. He is skilled in translating investigative information into causation opinions, connecting dose, biomarker significance, and clinical outcome—for poisoning, occupational, environmental, and mass-casualty toxicology cases.

Areas of Expertise:

Dr. Glenn Prestwich  is a National Academy of Inventors fellow with over 45 years of experience as a professor, entrepreneur, and biotech startup C-suite executive. Dr. Prestwich specializes in Biomedical Intellectual Property. He has been a prolific inventor since 1977, and an expert witness in IP law cases since 2007. He is an inventor on over 95 patents and patent applications, including 48 issued patents.

Litigation Support - Dr. Prestwich brings to all legal and technical cases a deep appreciation for how chemistry informs the invention and development of products that offer solutions to problems in the life sciences and medicine, ranging from disease detection and treatment to tissue healing and regeneration. He’s been involved in intellectual property litigation that concern medical devices, diagnostics, new pharmaceuticals, drug delivery, agrochemicals, and consumer products.

As an expert witness, Dr. Prestwich enjoys the challenges of dissecting the validity (or invalidity) of patents in litigation. He appreciates the subtleties of claim construction and works collaboratively with attorneys to identify successful arguments based on sound science and legal principles. He has drafted over 40 expert reports, declarations, and affidavits in support of his attorney clients.  He has been deposed 18 times and testified in Court four times.

Glenn D. Prestwich on Accessible and Experienced Expert Witnesses

Areas of Expertise:

Publications - Dr. Prestwich is an organized, clear, and effective writer. He has co-authored  over 610 additional peer-reviewed articles in the scientific literature, and written over 50 single-author scientific publications, reviews and book chapters. His publications encompass areas such diverse topics as anti-cancer drugs, gels for wound repair, cell therapy, and regenerative medicine, insect and pest control agents, cholesterol-lowering agents, lipids and cell signaling tools, and anti-inflammatory agents.

Douglas L. Seemann, BCE,  is a Board Certified Entomologist (BCE) with expertise in Applied Forensic Urban Entomology and Pest Control Practices, having been retained in over 200 cases. He holds several Pest Control Licenses in California and Arizona, and an active Real Estate Broker license. Mr. Seemann recently held the Qualifying licenses for 2 southern California pest control companies and an Arizona School District. He previously held licenses in Connecticut, New York and New Jersey and additionally managed pest control branches in New Mexico, Texas, Nevada, and Sonora Mexico.  

A graduate of the University of Connecticut where he focused on medical entomology and parasitology, Mr. Seemann has served as Technical Director, Manager, VP and Owner of Pest Control companies across the country since 1983, and is currently the Technical Director of a pest control company in Arizona.

Mr. Seemann has been a consultant since 2000 and served as the Arizona Governor's appointed State Entomologist Advisor to the Arizona Office of Pest Management, and is on the BCE Continuing Education Committee for the Entomological Society of America. He was one of the authors of the Arizona State Pest Control Certification Manual, has written numerous articles in the trade publications, and taught Pest Management as Associate Professor at the State University of New York. 

Litigation Support - Douglas Seemann has served as an expert witness in numerous cases and has found that these cases rarely go to trial and typically result in a settlement once the conclusions and the supporting data are presented. If it does become necessary to appear in court or deposition, he is well prepared and qualified to do so with extensive public speaking, educational, and instructive experience. With dozens of depositions and numerous appearances in court, Douglas Seemann, BCE is ready to assist you in representing your client.

Mr. Seemann has represented both Plaintiffs and Defendants in numerous civil cases. To date, in cases where he was allowed to testify, nearly all of his clients have won their cases, or received a favorable settlement. 

Areas of Expertise: