Why Trust This Analysis
This article is part of our ongoing no-fault coverage, with 271 published articles analyzing no-fault issues across New York State. Attorney Jason Tenenbaum brings 24+ years of hands-on experience to this analysis, drawing from his work on more than 1,000 appeals, over 100,000 no-fault cases, and recovery of over $100 million for clients throughout Nassau County, Suffolk County, Queens, Brooklyn, Manhattan, and the Bronx. For personalized legal advice about how these principles apply to your specific situation, contact our Long Island office at (516) 750-0595 for a free consultation.
The Foundation of Expert Testimony: Why Data Matters
In legal proceedings, expert witnesses play a crucial role in helping courts understand complex technical matters. However, their opinions must be grounded in reliable methodology and supporting data to have any legal weight. A recent Fourth Department case illustrates what happens when an expert fails to provide the foundational data underlying their conclusions.
The case of Costanzo v County of Chautauqua serves as an important reminder that expert affidavits must do more than simply state conclusions. Courts require experts to demonstrate the factual basis for their opinions, particularly in technical fields like accident reconstruction. This requirement ensures that expert testimony meets the standards of reliability and scientific validity that our legal system demands.
When experts fail to provide supporting data, their testimony becomes speculative and loses its probative value. This principle applies across various areas of litigation, from causation determinations to complex insurance fraud cases involving medical opinions.
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Costanzo v County of Chautauqua, 2013 NY Slip Op 06475 (4th Dept. 2013)
“The County’s cross motion was based in part on the affidavit of a transportation engineer who offered his opinion as an accident reconstruction expert. We conclude that the affidavit was speculative and conclusory inasmuch as the expert failed to submit the data upon which he based his opinions, and thus the affidavit had no probative value”
The issue of substantiating an opinion with the data that the opinion is predicated upon is an interesting topic.
Key Takeaway
This decision underscores a fundamental principle in litigation: expert opinions must be supported by underlying data and methodology to have legal significance. Courts will not accept conclusory statements, even from qualified experts, when the factual foundation is absent. Attorneys must ensure their experts provide comprehensive documentation supporting their conclusions to avoid having critical testimony excluded or deemed valueless.
Legal Update (February 2026): Since this post’s publication in 2013, New York courts have continued to develop standards for expert testimony admissibility, particularly regarding data foundation requirements and methodological reliability in no-fault insurance litigation. Practitioners should verify current case law developments and any updated evidentiary standards that may affect expert witness requirements in personal injury and insurance disputes.
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Legal Context
Why This Matters for Your Case
New York's no-fault insurance system, established under Insurance Law Article 51, is one of the most complex insurance frameworks in the country. Every motorist must carry Personal Injury Protection coverage that pays medical expenses and lost wages regardless of fault, up to $50,000 per person.
But insurers routinely deny valid claims using peer reviews, EUO scheduling tactics, fee schedule reductions, and coverage defenses. The Law Office of Jason Tenenbaum has handled over 100,000 no-fault cases since 2002 — from initial claim submissions through arbitration before the American Arbitration Association, trials in Civil Court and Supreme Court, and appeals to the Appellate Term and Appellate Division. Jason Tenenbaum is one of the few attorneys in the state who both writes his own appellate briefs and tries his own cases.
His 2,353+ published legal articles on no-fault practice are cited by attorneys throughout New York. Whether you are dealing with a medical necessity denial, an EUO no-show defense, a fee schedule dispute, or a coverage question, this article provides the kind of detailed case-law analysis that helps practitioners and claimants understand exactly where the law stands.
About This Topic
New York No-Fault Insurance Law
New York's no-fault insurance system requires every driver to carry Personal Injury Protection (PIP) coverage that pays medical expenses and lost wages regardless of who caused the accident. But insurers routinely deny, delay, and underpay valid claims — using peer reviews, IME no-shows, and fee schedule defenses to avoid paying providers and injured claimants. Attorney Jason Tenenbaum has litigated thousands of no-fault arbitrations and court cases since 2002.
271 published articles in No-Fault
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Disclaimer: This article is published by the Law Office of Jason Tenenbaum, P.C. for informational and educational purposes only. It does not constitute legal advice, and no attorney-client relationship is formed by reading this content. The legal principles discussed may not apply to your specific situation, and the law may have changed since this article was last updated.
New York law varies by jurisdiction — court decisions in one Appellate Division department may not be followed in another, and local court rules in Nassau County Supreme Court differ from those in Suffolk County Supreme Court, Kings County Civil Court, or Queens County Supreme Court. The Appellate Division, Second Department (which covers Long Island, Brooklyn, Queens, and Staten Island) and the Appellate Term (which hears appeals from lower courts) each have distinct procedural requirements and precedents that affect litigation strategy.
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