Chemistry: Clinical Chemistry/Biochemistry - Chemical Pathology Expert Witnesses: 6

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.

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:

Kirk DeLeeuw is a highly regarded and accomplished Forensic Biology and DNA Consultant / Expert Witness both nationally and internationally. He has over 20 years of dedicated experience in Molecular Biology and Forensic Science and is well respected worldwide.

Mr. DeLeeuw's career is defined by a deep technical mastery of DNA analysis, including specialized expertise in interpreting complex multi-contributor samples using Probabilistic Genotyping Software (PGS) such as STRmix. Mr. DeLeeuw is licensed by the Texas Forensic Science Commission. He likewise has a comprehensive understanding of FBI Quality Assurance Standards (QAS) and ISO/IEC 17025 accreditation requirements. He applies the standards through meticulous auditing of case files, bench notes, and high-volume electronic data files and images.

Litigation Support - Beyond the laboratory, Mr. DeLeeuw is a seasoned Expert Witness, qualified to provide testimony in Body Fluid Identification / Serology and DNA Analysis across numerous jurisdictions. He has provided sworn affidavits and oral testimony in federal, circuit, and district courts in many states including Washington DC, and internationally in the Royal Turks and Caicos Islands. His ability to translate sophisticated molecular biology data into clear, accessible testimony ensures that scientific integrity remains paramount during both civil and criminal litigations.

Mr. DeLeeuw maintains technical proficiency through a rigorous commitment to continuing education, frequently attending the International Symposium on Human Identification and National CODIS Conferences. His hands-on experience spans a wide array of instrumentation, including Applied Biosystems Genetic Analyzers and Hamilton robotic workstations, as well as various quantification and amplification kits. This combination of technical expertise, regulatory knowledge, and proven courtroom experience allows him to provide unparalleled oversight and analysis in the field of forensic DNA.

Areas of Expertise:

Background Experience - Mr. DeLeeuw's extensive professional background includes high-level roles across private and public sectors. As a Forensic DNA Analyst at DNA Labs International, he analyzed casework from across the United States and internationally, utilizing advanced PCR/STR-based methods and various chemistries. Prior to that, he served for nearly 20 years as a Forensic Scientist for the Michigan State Police.

Ryan Larrison is a senior forensic science and public sector executive with over 25 years of experience spanning Forensic Laboratory Operations, Quality Assurance, Firearms Examination, and large-scale Program and Systems Management within the Michigan Department of State Police.

Mr. Larrison currently serves in a senior leadership role within the Information Technology Division, where he directs a multi-million-dollar portfolio of enterprise systems, operations, and project delivery. In this capacity, he oversees complex, multi-agency initiatives, aligning technical execution with operational and investigative outcomes across multiple state departments. His work includes executive sponsorship of statewide technology programs and the coordination of vendors, stakeholders, and cross-functional leadership teams in high-risk, high-visibility implementations.

Litigation Support - Mr. Larrison serves as an expert witness in cases involving laboratory analysis or laboratory quality assurance. He has been deposed and/or testified over 200 times in the past 5 years.

Areas of Laboratory Expertise:

Background Experience - Prior to his current role, Mr. Larrison served as Assistant Division Director and Quality Assurance Manager for the Michigan State Police Forensic Science Division. In that role, he was responsible for the strategic direction, implementation, and oversight of quality systems across seven accredited forensic laboratories. He led all quality assurance activities, including training, corrective action programs, risk assessment frameworks, and accreditation compliance under ISO 17025 standards. His leadership resulted in a substantial reduction in non-conformities and sustained accreditation across all laboratory operations. 

Mr. Larrison has extensive experience as a program executive and project sponsor for complex forensic and evidential systems. He directed the statewide implementation of the Evidential Breath Alcohol Testing Program, including instrument selection, software integration, vendor coordination, and regulatory compliance, supported by a $2.5 million procurement process. He also led the development and implementation of a Forensic Genetic Genealogy program, establishing quality expectations, vendor deliverables, and investigative reporting standards.

Sara J. Schreiber, PhD, D-ABFT-FT, is a worldwide leader and highly accomplished Forensic Toxicologist, Educator, and Consultant whose work has earned recognition at both the national and international levels through leadership, teaching, professional service, and participation in major forensic pursuits.

Dr. Schreiber has more than two decades of experience in forensic science, including over 25 years in Toxicology and Controlled Substance Analysis, and has served in senior laboratory, technical director, academic, and expert roles in governmental forensic institutions.

Litigation Support - Dr. Schreiber provides comprehensive technical review and expert analysis in complex criminal and civil matters where alcohol, drugs, and poisons are at issue. Her work bridges the gap between advanced toxicological data and the courtroom by critically evaluating laboratory methods, case files, bench notes, instrumental data, and reports to determine whether testing, interpretation, and quality practices meet accepted forensic and accreditation standards, including ISO/IEC 17025, American Board of Forensic Toxicology (ABFT), and relevant professional guidelines. 

Dr. Schreiber draws on her experience as a diplomate of the American Board of Forensic Toxicology and her leadership roles in organizations such as MAFS, SOFT, NAME, OSAC, and TIAFT. When requested, she provides clear, accessible expert testimony, affidavits, and consultation to attorneys, investigators, and courts, translating complex toxicological and medicolegal issues into opinions that can be understood and evaluated by judges and juries.

Areas of Expertise: 

Background Experience - Dr. Schreiber’s national notoriety is reflected in her repeated invitations to lecture, train, and present on forensic toxicology, opioid deaths, toxicology trends, medicolegal death investigation, expert testimony, and related forensic topics for professional associations, public defenders, prosecutors, medical and university audiences, public health groups, and scientific meetings across multiple states throughout the US. Her work has also contributed to public-health and death-investigation initiatives through overdose fatality review teams, national overdose fatality review consulting, Department of Justice (DOJ), National Institute of Justice (NIJ), and the RTI Center for Forensic Sciences technology Working Group participation, and overdose-related strategy teams.

Gary D. Fletcher, PhD,  is the Founder and Principal Consultant at RnDDx Solutions LLC, a consulting firm founded in 2015, focused on Industrial Mechanical Engineering and Biomedical Engineering and Research and Product Development.  In his 30 years of experience, he has been co-inventor on 23 patents for devices and methods in blood collection and processing.

Litigation Support - Dr. Fletcher has subject matter expertise in Medical Device Mechanical Engineering and subject matter expertise in Medical Devices for blood and specimen collection and sample processing for in vitro diagnostics, point of care diagnostics, and therapeutics, including glucose monitoring. He serves as an expert witness in patent infringement cases involving medical device and diagnostic biomedical engineering, blood collection, separation, fluidic preparation, glucose monitoring, and cell therapy preparation devices.

Dr. Fletcher offers patent litigation services to law firms and lawyers supporting medical device and diagnostic industry clients, who need physical science and mechanical and biomedical engineering expertise for District Court, PTAB, and ITC patent cases. As an industry consultant, his ideal clients are R&D, product development, and innovation leaders in startup, emerging, and established medical device and diagnostic companies, who face product development and competitive challenges.

Areas of Expertise:

Dr. Fletcher is an entrepreneurial executive with expanding R&D roles in business, technology, and new product development leadership and execution, building and guiding teams in both Fortune 500 and startup companies. With a PhD in physics from Yale, he has a proven record of leadership in creating innovative new businesses and products in healthcare, medical devices, diagnostics, life, materials, and optical sciences.