Chemistry - Chemical Industry Expert Witnesses: 24

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.

As a Board-Certified Forensic Document Examiner (D-ABFDE) and Ink Chemist and Document Dating Specialist with over 33 years of experience, both Todd Welch and Gerry Laporte are world leaders in high-profile, extremely complex document cases.

Riley Welch LaPorte & Associates is the leading global forensic document firm, having conducted high-profile, multi-billion-dollar cases in the United Kingdom, France, Singapore, Hong Kong, Germany, Austria, Sweden, Canada, the Netherlands, Hungary, Israel, Switzerland, and Denmark. We are considered a top-tier firm, having conducted work for foreign governments, and are recognized globally by the most prominent law firms in the world for providing the highest level of forensic document examination services to both governmental and private entities.

Areas of Expertise:

Committed to fostering education and promoting justice, both Todd Welch and Gerry Laporte contribute to the advancement of forensic science through leadership roles, including service on the BOD for the American Board of Forensic Document Examiners and American Society of Questioned Document Examiners; served as the 40th President of the Midwestern Association of Forensic Scientists (Welch); and served as members of the National Institute of Justice Forensic Science Technology Working Group.

Both Todd Welch and Gerry Laporte have testified as expert witnesses in numerous notable international ICSID cases (ICSID Case No ARB/06/8, ICSID Case No ARB/14/22, PCA Arbitration Case No 2020-21_The Hague) involving forensic document examination, handwriting analysis, ink dating, and forgery detection.

Their litigation support experience includes testifying before government officials, international tribunals, arbitrations, and mediations. Their testimony has been presented in courts worldwide handling a wide variety of legal matters including: defamation, investment law, insurance law, medical malpractice suits, will disputes, estate disputes, contract and patent disputes, trademark disputes, divorce disputes, and trade secrets cases.

Gerry Laporte and Todd Welch have international notoriety and have testified in major courts such as the International Centre for Settlement of Investment Disputes (ICSID), the Permanent Court of Arbitration (PCA) under UNCITRAL Rules, the International Criminal Court (ICC), the U.S. District Court for the Eastern District of New York, and appellate courts in Illinois and Washington, D.C., among others. Their involvement in high-stakes litigation across multiple geographical jurisdictions confirms their reputation and widespread professional acceptance worldwide.

Jennifer L. Naso is a board-certified Forensic Document Examiner with over two decades of experience in forensic science and questioned document examination. She has served as a Forensic Document Examiner with Riley, Welch, LaPorte & Associates since 2011, where she conducts examinations involving handwriting identification, signature authenticity, document alterations, indented writing, obliterations, document authentication, printing processes, and other aspects of forensic document analysis. In addition to conducting casework, she provides technical reviews of examinations completed by other forensic document examiners.

Prior to joining Riley, Welch, LaPorte & Associates, Ms. Naso served as a Document Analyst with the United States Secret Service (USSS), where she successfully completed the agency's rigorous Questioned Document Examiner Training Program. During her tenure with the Secret Service, she conducted examinations in support of criminal investigations involving handwriting, questioned documents, and counterfeit materials. 

Consultants. Experts. Innovators.™

Operating from more than 110+ offices around the globe, we provide services to corporations, insurance companies, law firms, and government agencies.

Rimkus Life Sciences experts have a wealth of specialized expertise to help clients comprehend and improve how humans interact with their facilities, products, and systems.

Our experts offer significant professional experience related to studying and understanding human behavior and experience. Our experts have extensive knowledge involving but not limited to human health and medical devices, warnings and signage, perception and reaction, medicine and patient care, and health and sports activity.

The scientists, engineers, and researchers in Rimkus Life Sciences specialize in human based research to support product design and development, product validation, and development of instructions and warnings for use. Our experts work with clients across the globe in every major product sector. They understand how to leverage rigorous research and thoughtful analysis with creative problem solving to support the development of products.

Rimkus Global Services Overview

LIFE SCIENCE EXPERTISE

Biomedical Engineering

Human Factors

Legal Nurse Consulting

Product Safety

Sports Science Consulting

Toxicology Food Safety

View our full suite of Life Sciences Expert Services.

GLOBAL OFFICES

Rimkus operates from 110+ offices worldwide, with headquarters in the following cities.

View a full list of Rimkus Office Locations.

View Rimkus Quantum and Delay Expert Services Profile.
View Rimkus Forensic Expert Services Profile.

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.

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:

George Schiro is a DNA Technical Leader - Forensic Scientist. His duties include incorporating the DNA Advisory Board (DAB) standards, accountability for the technical operations of the lab, conducting DNA analysis using the 13 STR core loci and Y STR in casework, DNA research, forensic science training and crime scene investigation.

Mr. Schiro has worked over 3500 cases and has qualified as an expert over 175 times in 31 Louisiana parish courts, Arkansas, California, Florida, Mississippi, Missouri, Nevada, New York, Texas, West Virginia, federal court, U.S. court-martial, and two Louisiana city courts. Has also consulted on cases in 29 states.

Qualified as an Expert in the Following Areas:

Professor Christopher J. Tennant, PhD, CIH, has over 40 years of experience in the field of Environmental Health and Industrial Hygiene. He is Board Certified in the Comprehensive Practice of Industrial Hygiene. Dr. Tennant is currently President, CEO, and Principal Consultant at San Joaquin Environmental, in Fresno California, where he consults with Federal, State, County, City, various public agencies, and private industry sectors from public housing to Aerospace. His services are available in all 50 US States and the United Kingdom.

Dr. Tennant also serves as Professor Emeritus for the Department of Public Health at Fresno State University where he's taught Environment Health, Industrial Hygiene, and Occupational Health and Safety for 35 years at both undergraduate and post graduate levels.

Litigation Support - Dr. Tennant has been retained by numerous insurances companies and law firms on various Industrial Hygiene matters throughout the US, including workers compensation, property damage, personal injury, and wrongful death. He has testified as an expert witness in Federal Court, Superior Court, and Workers Compensation Appeals Board over 100 times. He's been deposed many more times. 

Areas of Expertise: