Expert Witness
Rudolph Johnson, PhD — Toxicology Expert Witness
Rudolph Johnson, PhD
"When the lab results tell a story you didn't expect, call me."
Who I Work With
- Toxic tort litigators who need expert insight into what the toxicology evidence actually means
- Public defenders who need an independent expert to examine laboratory results.
- Attorneys handling a case where drug or alcohol lab testing could be decisive
Key Documents
Areas of Expertise
Dr. Johnson's opinions are rooted in hands-on scientific experience — not theory.
Toxicology
Expert in forensic and clinical toxicology, drug metabolism, pharmaceutical toxicity, biomarkers, and pharmacokinetics — with direct application to criminal, civil, and regulatory matters.
Examining Lab Results
Expert identification and analysis of discrepancies between laboratory test results, chain-of-custody records, and reported findings. Authority on laboratory accreditation, CLIA compliance, analytical validity challenges, and false positive/negative determinations. When laboratory results are in question, Dr. Johnson is the expert to call to examine them.
Environmental Toxicology
Expert analysis of PFAS, heavy metals, VOCs, pesticides, and industrial contaminants in human biospecimens, water, and soil.
Qualifications
Current & Recent Positions
UW School of Medicine & Public Health — 2025–Present
University of Wisconsin–Madison
U.S. Department of Veterans Affairs — 2023–2025
CDC, Division of Laboratory Sciences — 2013–2023
Tulane University School of Professional Advancement
Professional Memberships & Editorial
Journal of Analytical Toxicology
Active Member
Active Member
Analytical chemistry, public health toxicology, emergency laboratory preparedness
Biomedical laboratory testing contributor, The Hague, Netherlands
Academic Foundation
Analytical Chemistry
Purdue University
Studied under Dr. R. Graham Cooks, a world-recognized pioneer in mass spectrometry. Dissertation focused on real-time chemical detection — the foundational technology behind modern chemical agent identification.
Pharmaceutical Sciences — Clinical Toxicology
University of Florida, College of Pharmacy
Concentration in clinical toxicology. Provides direct expertise in drug metabolism, pharmacokinetics, clinical biomarkers, and pharmaceutical toxicity relevant to exposure litigation.
Experience in Good Automated Laboratory Practices
Virginia Military Institute
Undergraduate training in laboratory science and instrumentation automation, providing a rigorous technical foundation for advanced graduate study in analytical chemistry.
Retain Dr. Johnson
Forense LLC is the legal entity through which Dr. Johnson's expert-witness practice operates. Engagements, correspondence, and contact details are managed at chemwitness.com.
Dr. Johnson is available for expert witness engagements, litigation consulting, and preliminary case assessments. Inquiries are confidential and subject to conflict-of-interest review.
Responses to initial inquiries are typically provided within two business days. Please provide a brief case description, jurisdiction, and anticipated role (plaintiff/defense) when reaching out.
What to Expect
- 01
Send a brief case description, jurisdiction, and your role (plaintiff or defense).
- 02
A conflict-of-interest check is completed — typically within one business day.
- 03
An initial consultation is scheduled to assess the toxicology issues at hand.