Cohen

David is a nationally recognized science counsel who vigorously defends product liability and toxic tort litigation.  As a member of the firm’s Pharmaceutical, Medical Device & Healthcare Litigation Group, he has led efforts to dismantle general and specific causation theories in high-stakes pharmaceutical, medical device, and environmental exposure litigations.  David has cross-examined more than 135 physicians and scientists at depositions and hearings, eliciting testimony to support Daubert/Frye challenges.  His team at Butler Snow includes lawyers with scientific degrees and a deep interest in the intersection of science, medicine, and the law.  In fast moving mass tort proceedings, David’s team works closely with national coordinating counsel, case work-up counsel, and other science counsel to formulate and implement effective medical defense strategies. 

David’s work has been recognized by The Legal 500 U.S., BL Rankings, The Best Lawyers in America®, Thomson Reuters Super Lawyers® and Who's Who Legal.

• Drug & Device Litigation
• Products, Catastrophic & Industrial Litigation
• Groundwater & Chemical Exposure Litigation
• Mass Torts

Pharmaceutical, Medical Device and Healthcare

Judicial Clerkship

• Law Clerk to Honorable D. Brook Bartlett, Western District of Missouri, Kansas City, 1986-1988  

Daubert/Frye Hearings and Arguments

• Monk vs. Johnson & Johnson, Hon. M. Rowland, Northern District of Illinois (Oral argument on motion to compel production of laboratory data from lymphocyte toxicity assay performed by plaintiff expert witness).
• Terry v. McNeil-PPC, Inc., McNeil Consumer Healthcare and Johnson & Johnson, Inc., Hon. L. Stengel, Eastern District of Pennsylvania (Oral argument on Daubert motion challenging the admissibility of plaintiff expert opinion testimony based upon data in the Acute Liver Failure Study Group registry).   
• Terry v. McNeil-PPC, Inc., McNeil Consumer Healthcare and Johnson & Johnson, Inc., Hon. L. Stengel, Eastern District of Pennsylvania (Oral argument on Daubert motions challenging the admissibility of plaintiff hepatologists opinion testimony on general causation). 
• Jackson v. McNeil-PPC, Inc., McNeil Consumer Healthcare and Johnson & Johnson, Inc., Hon. N. Johnson, Superior Court of New Jersey, Atlantic County (Oral argument at Kemp hearing in support of defendants’ Kemp motion challenging admissibility of plaintiff hepatologist opinion testimony on general causation).
• Lyles v. McNeil-PPC, Inc., McNeil Consumer Healthcare and Johnson & Johnson, Inc., Hon. N. Johnson, Superior Court of New Jersey, Atlantic County (Oral argument opposing plaintiff Kemp motion challenging admissibility of hepatologist opinion testimony).
• Baxter v. Lincoln Electric Co., Hon. J. Zouhary, U.S.D.C., Cleveland (Daubert motion to exclude treating neurologist testimony in welding fume litigation).
• Street v. Lincoln Electric Co., Hon. K. O’Malley, U.S.D.C., Cleveland (Daubert motion to exclude plaintiff movement disorder neurologist testimony in welding fume litigation). 
• Boyd v. Lincoln Electric Co., Hon. H. A. Hanna, Court of Common Pleas, Cleveland (evidentiary hearing and motion under Ohio law to exclude plaintiff movement disorder neurologist testimony in welding fume litigation). 
• Carn v. National Railroad Co., Hon. W. Manfredi, Court of Common Pleas, Philadelphia (oral argument under Pennsylvania law to compel FD-PET brain scan of plaintiff in welding fume litigation).
• Jerkins v. Lincoln Electric Co., Hon. K. O’Malley, U.S.D.C., Cleveland (evidentiary hearing and opposition to plaintiff’s Daubert motion challenging admissibility of defense neuroradiologist testimony on brain MRI in welding fume litigation). 
• Cooley v. Lincoln Electric Co., Hon. K. O’Malley, U.S.D.C., Cleveland (oral argument and Daubert motions to exclude testimony of multiple treating physicians in welding fume litigation). 
• White v. Alloy Rods. Corp., Hon. S. R. Ohmer, Missouri Circuit Court, St. Louis (oral argument and motion under Missouri law to exclude plaintiff expert neurologist testimony in welding fume litigation). 
• MDL Welding Rod Litigation, Hon. K. O’Malley, U.S.D.C., Cleveland (multiple oral arguments and Daubert motions to exclude plaintiff expert testimony and to oppose plaintiff Daubert challenges to defense expert testimony in welding fume litigation). 
• MDL Ephedra Litigation, Hon. J. S. Rakoff, U.S.D.C., Southern District of New York (evidentiary hearing and Daubert motion to exclude multiple plaintiff expert witnesses in ephedra dietary supplement litigation). 
• McMeekin v. Metabolife, Hon. J. Ellisor, 122nd Judicial District Court, Galveston County, Texas (video testimony and argument under Texas law to exclude testimony of pulmonologist in ephedra dietary supplement litigation).
• MDL Diet Drug Litigation, Hon. L. Bechtle, U.S.D.C., Philadelphia (Daubert motion and evidentiary hearing to exclude pharmacologist and toxicologist testimony in fen-phen diet drug litigation).
• Linnen v. AHP, et al., Hon. R. Brassard, Massachusetts Superior Court, Boston (motion and evidentiary hearing under Massachusetts law to exclude testimony of toxicologist in fen-phen diet drug litigation).

Pharmaceutical and Mass Tort Litigation

• Tylenol-ASD/ADHD - national science counsel to Kenvue defending claims in the Southern District of New York MDL that maternal ingestion of acetaminophen during pregnancy causes autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) in offspring.  As member of defense virtual science team, formulated medical defense strategies and worked up experts in ASD, ADHD, neurodevelopment, and acetaminophen toxicology.  Judge Denise Cote granted Kenvue’s Rule 702/Daubert motion excluding all plaintiff experts.
• Proceed/PVP Mesh MCL - national science counsel to Ethicon/Johnson & Johnson defending New Jersey consolidated proceeding alleging design defect and failure to warn claims arising from the surgical implant of Proceed and PVP mesh to repair abdominal wall hernias.  Developed medical defense strategies for the selection and discovery of cases and led a team of lawyers in the retention, vetting, and preparation of nationally recognized hernia surgeon experts, who submitted over 30 general and case specific expert reports addressing all aspects of ventral hernia repair, Proceed and PVP mesh, and discovery pool case fact issues.  
• Physiomesh MDL - national science counsel to Ethicon/Johnson & Johnson in multi-district litigation alleging claims of design defect and failure to warn from the implant of Physiomesh during ventral hernia repair surgery.  Assembled a team of nationally recognized hernia surgeons for the defense of the litigation, deposed plaintiff hernia surgeon Rule 26 expert witnesses, and prepared Daubert challenges to the admissibility of plaintiff expert opinions. 
• Tylenol SJS-TEN Litigation - science counsel for Johnson & Johnson defending claims that Tylenol and Motrin caused SJS/TEN in pediatric plaintiff.   Coordinated Rule 26 reports from dermatologist, pediatric infectious disease physician, epidemiologist, and clinical pharmacologist.  Cross examined plaintiff burn surgeon, toxicologist, and pharmacologist expert witnesses on issues of SJS/TEN epidemiology, general and specific causation, and the lymphocyte toxicity assay.  
• Propecia Litigation – national science counsel to Merck defending MDL and New Jersey coordinated proceedings alleging male sexual dysfunction and cognitive complaints from Propecia (finasteride 1 mg) use for male pattern hair loss.  Coordinated the production of Rule 26 reports from experts in epidemiology, endocrinology, psychiatry, dermatology, and basic science.  Cross-examined plaintiff expert witnesses in male sexual medicine, epidemiology and biochemistry, and prepared Daubert motions to exclude plaintiff expert opinions on general and specific causation in first four MDL bellwether cases.
• Tylenol ALF Litigation – national science counsel to McNeil/Johnson & Johnson defending MDL and New Jersey coordinated proceedings alleging acute liver failure from low dose Tylenol ingestion.  Provided expert witness resources, cross-examined 12 treating hepatologists and gastroenterologists and plaintiff expert witnesses, prepared and argued Kemp and Daubert motions, and conducted third-party discovery on the ALFSG registry. 
• Manganese Welding Fume Litigation - national science counsel to an industry group defending toxic tort litigation consisting of approximately 20,000 claims alleging manganism and other neurological injuries from exposure to manganese compounds in welding fume. The federal litigation was consolidated into an MDL in the Northern District of Ohio, and significant litigation occurred in the state courts of Mississippi, Texas, Louisiana, Arkansas, West Virginia, Ohio, Illinois, and California. Provided expert witness resources, cross-examined more than 50 treating neurologists and expert witnesses, and presented evidence and arguments at Daubert hearings.
• Metoclopramide Litigation - national science counsel to a group of pharmaceutical companies defending mass tort litigation alleging that the drug causes tardive dyskinesia and other involuntary movement disorders.
• Ephedra Litigation - national science counsel for consumer product companies defending mass tort litigation alleging stroke, heart attack, cardiac arrest, and other injuries. Conducted Havner hearing in Galveston, Texas and MDL Daubert hearing in the Southern District of New York.
• Phentermine Litigation - national science counsel to a pharmaceutical company in the “fen-phen” diet drug litigation alleging primary pulmonary hypertension and cardiac valve disease. Conducted Daubert hearings in Massachusetts state court and at the MDL proceeding in the Eastern District of Pennsylvania.
• Methylphenidate Litigation - science counsel to a pharmaceutical company in cases alleging addiction and violent adolescent behavior from the misuse of the drug filed in Alabama and Mississippi state courts.
• Flu Vaccine Litigation - science counsel to a pharmaceutical company in cases alleging the development of Guillain-Barré syndrome following influenza vaccination filed in New Hampshire and other state courts.

Other Product Liability Cases

• Medical Screening Test Case -  Science counsel for international company and laboratory in wrongful death case in South Carolina state court involving a medical screening test.  Identified and retained experts in colorectal surgery, oncology, and gynecological office practices, formulated medical defense strategies, and deposed plaintiff’s medical oncologist.
• Ice Pack Burn Case - Science counsel to medical device company defending claims in New York State Supreme Court of injuries arising from a clinic’s application of commercial ice packs to a patient’s bare skin following a procedure with the company’s device.  At depositions of plaintiff’s treating physicians, elicited testimony to support a defense motion for summary judgment.  The Appellate Division, First Department reversed the trial court’s denial of the motion and dismissed the company from the case.
• Pulmonary Fibrosis Case - science counsel to a manufacturer in a case alleging pulmonary fibrosis from occupational exposure to iron fume filed in New York State Supreme Court.
• Parkinson’s Disease Case- science counsel to an insurer defending claim that kiln fume causes Parkinson’s disease filed in New York State Supreme Court.
• Colon Cancer Case - science counsel to estate in case filed by the Department of Justice challenging the opinions of treating oncologists on the expected survivorship of a Stage IV cancer patient filed in the Western District of Washington.

• The Legal 500 U.S.
  • Recognized in the editorial for nationwide Dispute Resolution: Product Liability, Mass Tort and Class Action: Pharmaceuticals and Medical Devices – Defense, 2013; 2015; 2019.
• BL Rankings, The Best Lawyers in America®
  • Product Liability Litigation – Defendants, 2013-2026
• Thomson Reuters Super Lawyers®
  • New York Metro Lawyers – 2006-2012, 2016-2019
• Who's Who Legal, Product Liability Defence, 2020-2021

• New York, 1986
• U.S. District Courts
• New York: Eastern, Southern
• U.S. Court of Appeals
• 2nd Circuit
• 3rd Circuit
• U.S. Supreme Court

• Fordham University, J.D., 1986
• Union College, B.A., History, magna cum laude, 1983
  • Phi Beta Kappa
• London School of Economics and Political Science, 1981

• Clerkship, Honorable D. Brook Bartlett, Western District of Missouri, Kansas City, 1986-1988

• Product Liability Advisory Council (PLAC)
  • Sustaining Member
• American Bar Association
  • Section of Litigation
  • Section of Science and Technology Law
• Defense Research Institute (DRI)

• Co-Author, “Turning Up the Heat? Pressure Testing Scientific Theories in Science Days, Rule 702 Hearings, and the Hot Tub,” Pro Te: Solutio, Vol. 18, No. 1, March 2025.
• Co-Author, "The COVID Trilogy: The One About the Pandemic," Pro Te: Solutio, Vol. 14, No. 2, June 2021.
• Author, “The Science of Storytelling in the Storytelling of Science,” Pro Te: Solutio, Winter 2017.
• Co-Chair, "How to Avoid Getting Sliced by Cutting-Edge Developments in Expert Witness Challenges," Daubert Practice 2013, Practising Law Institute, New York, September 2013.
• Panelist, "Case Study of Welding Fume Litigation: Getting the Best Result at Trial By Working with CoDefendants," ACI’s 4th National Forum on Chemical Products Liability and Environmental Litigation, Chicago, April 2013.
• Faculty Member, "Expert Witnesses at Trial," Practising Law Institute, New York, January 2011, January 2012, & June 2013.
• Author, "Battle Of The ‘Experts’: Daubert And Milward," Product Liability Law360 and Appellate Law360, January 2012.
• Faculty Member, "Out of the Fryeing Pan, Into the Hearing," State of New York Unified Court System Judicial Seminar, New York, July 2002 (Invitation from the Honorable Alan D. Oshrin, J.S.C.).
• Panelist, "Litigating Kumho Tire, Daubert, and Frye in State and Federal Courts," New York State Bar Association Seminar, New York, April 2002.
• Lecturer in Residence, "Daubert and Mass Tort Litigation," Valparaiso University School of Law, Valparaiso, Indiana, March 2002.
• Session Chairperson and Speaker, "Scientific Evidence in the Courtroom: A Strategic Overview for Pharmaceutical Professionals," 37th Annual Meeting, Drug Information Association, Denver, July 2001.
• Co-Author, "Tiptoeing Through Mass Tort Litigation," Risk Management Magazine, April 2001.
• Author, "Expert Witnesses," Marino Institute for Continuing Legal Education, New York, December 2000.