Construction Law Section

Asking Why: Taking Expert Depositions with the Goal of Striking Expert Evidence

By NJSBA Staff posted 04-15-2020 10:35


Editor’s Note: The following article by Thomas J. Cotton was published as part of the Construction Law Section Newsletter Vol. 21, No. 2, which was distributed to members of the Construction Law Section. To learn more about joining a section of the New Jersey State Bar Association, email us at [email protected]

Every parent knows that toddlers are quick to question every “expert opinion” with which they are presented. “Why does the dog get to sleep outside?” “Why does Dad get to eat pizza for breakfast?”

There is wisdom in a toddler’s unrelenting questioning. Or at least, there is a litigation strategy. Many litigations either require or make use of expert evidence. This is especially true in construction litigations. Denying your adversary a proffered expert can oftentimes be a fatal blow. But before you can swing that haymaker, you are well-served to pepper the expert at a deposition with unrelenting “Why?” questions.

This article outlines the general requirements for expert opinion to be admitted as evidence and presents strategies for opposing admissibility, within the context of a construction litigation and within the realm of the expert’s deposition, by offering go-to questions to prime net-opinion motions.

Background on Expert Evidence in Construction Litigations

Expert evidence is a common feature in construction litigations. Lawsuits arising from design defects feature architecture and engineering experts. Lawsuits arising from mismanagement feature delay experts. Anytime repairs or rebuilds are required, experts on cost estimation are not far away.

The prevalence of experts can cause construction litigators to overlook the fundaments of evidence. That youused similar experts (or even the same expert) in similar cases is immaterial. Expert evidence, like all evidence, must satisfy certain standards to be admissible.

Among those standards for admitting expert evidence, “(1) the intended testimony must concern a subject matter that is beyond the ken of the average juror; (2) the field testified to must be at a state of the art such that an expert’s testimony could be sufficiently reliable; and (3) the witness must have sufficient expertise to offer the intended testimony.”1 The expert’s opinion must also be based on “facts or data” that are “of the type reasonably relied upon by experts in the particular field.”2

Asking Why

Asking why is the first step toward the preclusion of expert evidence as net opinion. “Simply put, the net opinion rule ‘requires an expert to give the why and wherefore of his or her opinion, rather than a mere conclusion.’”3 The net opinion rule “forbids the admission into evidence of an expert’s conclusions that are not supported by factual evidence or other data.”4 There are four lines of questions that are typically available to a construction litigator who is hoping to present an adversary’s expert evidence as net opinion.

First, test the authorities that support the opinion. If the expert has an opinion on the standard of care for a design professional, then the expert must be able to connect that opinion to a foundation in the law (e.g., statute, case law, regulation), industry guidance (e.g., trade association presentation on best practices), or academic literature (e.g., scholarly articles).5 If the expert is unable to do so, then the expert’s opinion is arguably a personal “rule of thumb” and inadmissible net opinion.6

But don’t just ask what the authorities are; ask why they are authorities. Why are the items identified by the expert accepted by the expert’s field? If it is a trade association article, how frequently does the association review its guidance? If the expert drew their opinion from case law, what kind of legal research did the expert perform to confirm the soundness of that case law? Which version of the regulation did the expert review, because is the expert aware that the regulation has been amended twice in the past four years?

Second, test the reliability of the data forming the basis for the opinion. There are plenty of opportunities for this in a construction litigation. An architect expert who relies on measurements taken by a junior technician at the architecture firm will be hard-pressed to testify, with absolute certainty, that the measurements are free from any semblance of doubt. The expert could be questioned about whether they ever personally observed the technician’s techniques at other sites and audited them for accuracy. The expert could also be questioned whether the technician personally compared the final report’s underlying data to the field notes from which the report drew its data, to confirm the absence of disparities.

Third, test the sufficiency of the data forming the basis for the opinion. This focuses less on the data the expert did present and more on what the expert failed to consider. A construction expert who opines that the project manager’s deficient recordkeeping practices caused delays should be questioned about the prevalence of those same practices. More specifically, the expert can be asked what percentage of project managers keeps records in the same manner. The questioning should be unrelenting. If the expert claims this information is not needed, follow up with questions on how the expert can make that conclusion (e.g., Has the expert performed any comparative studies that determined this information is statistically insignificant?).

Fourth, test the strength of the expert’s opinion visà-vis the other opinions in the case.7 Why are you, the defense expert, reaching a different decision than the plaintiff expert? If the expert did anything differently to reach their opinion, then that difference should be met with an immediate, “Why?” 

A Straightforward Tactic

Asserting the net opinion rule is just one of many techniques for attacking an adversary’s expert. The expert’s insufficient expertise can be highlighted, the expert’s bias can be explored, or the expert’s field and methods can be assailed as non-scientific.

What makes a net-opinion strategy effective is how straightforward it is in practice: Just. Ask. Why. Even a toddler can do it. Indeed, toddlers would excel at turning an expert’s deposition testimony into a net-opinion motion. Two hours of questioning by this author’s 2-year-old daughter would likely be enough for experts to concede that their conclusions are net opinions, or to concede whatever else it takes to get her questioning to stop.

Thomas J. Cotton is an associate with Schenck, Price, Smith & King, LLP. He is a commercial litigator who represents clients in the construction, entertainment, and technology industries. His practice also includes employment litigation, professional liability, and high-stakes appeals.


  1. State v. Kelly, 97 N.J. 178 (1984).
  2. N.J.R.E. 703.
  3. State v. Townsend, 186 N.J. 473, 494 (2006) (quoting Rosenberg v. Tavorath, 352 N.J. Super. 385, 401 (App. Div. 2002)).
  1. Ibid.
  2. See Taylor v. DeLosso, 319 N.J. Super. 174, 180 (App. Div. 1999) (“The problem is that Courter presented no authority supporting his opinion. No reference was made to any written document, or even unwritten custom or practice indicating that the consensus of the architectural community recognizes a duty to make a site inspection for ‘small sites.’”).
  1. See Davis v. Brickman Landscaping, Ltd., 219 N.J. 395, 410 (2014) (deeming a putative expert’s finding, that fire sprinkler inspectors failed to identify deficiencies in the system’s design, to be net opinion because the building code provisions the expert cited did not speak to design-related issues).
  1. See Gore v. Otis Elevator Co., 335 N.J. Super. 296, 303-04 (App. Div. 2000) (taking issue with the expert’s opinion regarding an elevators allegedly negligent maintenance, given that the expert had failed to rule out potentially negligent design).