By: John P. Paone, Jr. and John P. Paone, III*

If you engage in complex matrimonial litigation, you will need to know how to cross-examine expert witnesses.  The ability of family law practitioners to cross-examine experts effectively is not simply a matter of trial skill.  While trial skill is needed, a large part of being able to successfully confront an expert is the result of extensive pretrial preparation. This article will serve as a road map for successfully challenging an adverse expert at trial.


 Commencing with the initial consultation, the family law practitioner must identify any and all issues which may require involvement of experts.  There are many areas of family law which may require experts, including health care professionals who render opinions on parenting time and child custody; forensic accountants who determine the cash flow and fair value of a business; occupational experts who assess the potential employability of a party and opine on that party’s ability to earn; medical experts who determine whether a party is disabled and cannot be employed for health reasons; and a vast array of appraisers who may value real estate, pensions, jewelry, artwork, wine, coins, stamps, guns, sports memorabilia, antique furniture, exotic vehicles, boats, planes, and a whole host of marital property.[1]

Complex divorce matters are cases most likely to result in trial and at trial cross-examination is the “greatest legal engine ever invented for the discovery of the truth.”  California v. Green, 399 U.S. 149, 158 (1970). Knowing the facts of your case and identifying the underlying issues will enable you to anticipate and understand the expert testimony likely to be presented. Once you identify the potential experts likely to be involved in your matter, you can begin the process of preparing for the day when you will confront these experts on cross-examination.


There is no excuse for being caught off guard by the testimony of an expert witness. The rules of discovery provide ample avenues to identify experts and to familiarize yourself with their opinions.  Interrogatories are essential to finding out whether the adverse party has retained an expert and whether that expert may be called as a witness at trial.  Pursuant to R. 4:10-2(d)(1), a party through interrogatories can require the adverse party to disclose the names and addresses of the experts expected to be called at trial.[2]  Interrogatories may also require experts to furnish a copy of their reports.  R. 4:17-4(a).[3] Expert reports must contain a complete statement of the expert’s opinions and the rationale for those opinions, the facts and data considered in forming the opinions, the qualifications of the expert (including a list of all publications authored within the preceding ten years), and terms of compensation for the report and testimony. R. 4:17-4(e).


Will you be confronting a single joint expert, the court’s expert, or the expert retained by the adverse party? In many cases, the expert is either selected jointly by the parties or appointed by the court.  The benefits of having a common expert include reducing fees, since the parties will likely share the cost of the joint or court expert rather than spending money on two experts to address the same issues.  There is also the thought that having a joint or court expert will expedite a resolution. This is because the parties are receiving one opinion rather than being confronted with conflicting expert opinions which may invite further litigation.

However, the reality is that a joint or court expert is not appropriate in every case.  Furthermore, even when hiring a joint expert makes sense, this does not preclude a dissatisfied client from challenging that expert’s opinions at trial or from hiring their own expert.  R. 5:3-3(h). Practitioners should be aware that pursuant to R. 5:3-3(g), the court-appointed expert “shall be subject to the same examination as a privately retained expert and the court shall not entertain any presumption in favor of the appointed expert’s findings.”  By analogy, the same principle should pertain to the testimony of a joint expert, especially if the parties did not agree in advance to be bound by the opinion of the joint expert.[4]  In short, don’t let your guard down thinking that you may not be called upon to challenge or defend the expert’s opinion simply because the expert was jointly retained or appointed by the court.


Does the expert possess the appropriate credentials that qualify him to render an opinion on the issue in dispute?  Does the expert maintain the appropriate state license or certification to provide expert testimony in a given field?  By way of example, the State Real Estate Appraiser Board licenses a Certified Residential Real Estate Appraiser to appraise residential units and vacant land used for family purposes. A Certified General Real Property Appraiser, on the other hand, may appraise all types of property.  The point being, all expert credentials and licensures must be explored by the practitioner.

Has the expert’s license ever been suspended or has the expert been sanctioned by a disciplinary authority? Efforts to obtain such information can be made by contacting the appropriate licensing bodies. Even assuming that the expert possesses the requisite qualifications and credentials to testify, counsel must question whether it is appropriate for the expert to do so?  Often, we see parties designate their personal business accountant or personal therapist as a testifying expert. Such experts come fraught with issues of bias and conflict ripe for cross-examination. In some cases, the expert’s code of ethical conduct may bar his involvement in the case.  For example, in a child custody case, a mental health professional who is a member of the American Mental Health Counselors Association may be serving in a clinical role by providing treatment to a party and child in family counseling.  Under this fact pattern, it would be inappropriate for this mental health professional to act as a forensic expert.  To do so would violate the counselor’s code of conduct prohibiting counselors from evaluating, for forensic purposes, individuals they are currently counseling or have counseled in the past. Section I.D. 4(g), AMHCA Code of Ethics (2015). The attorney should be prepared to address issues of bias and ethical impropriety when individuals with apparent conflicts are offered as expert witnesses.


Consider hiring a consulting expert to review, critique, and discuss the adverse expert’s report.  Consulting experts can assist you in understanding both the subject matter and the significance of the opinions offered by the adverse expert.  The consulting expert will be able to point out weaknesses in the adverse expert’s report, and assist you with preparing effective cross-examination questions at trial.

In general, confidential communications offered by and delivered to a consulting expert will be protected. The adverse party may not discover facts known or opinions held by a consulting expert absent “exceptional circumstances” that would allow for discovery of that expert’s identity and opinion.  R. 4:10-2(d)(3); Graham v. Gielchinsky, 126 N.J. 361 (1991).  Whether it be for reasons of cost or convenience, family law practitioners often eschew hiring a consulting expert and use their testifying expert to critique and review the report of the adverse expert. Keep in mind that when the “testifying expert” takes on dual roles as both a testifying and consulting expert, the role of the expert becomes blurred and privileges against non-disclosure may be lost.[5]


To determine whether the adverse expert is indeed an expert, the Rules of Evidence require that the opinions must be based on “scientific, technical, or other specialized knowledge” which will assist the trier of fact in understanding the evidence or deciding a fact in consequence. N.J.R.E. 702.  In furtherance of this point, the three criteria for admitting expert testimony are as follows: “(1) the intended testimony must concern a subject matter that is beyond the ken of the average juror [or layperson]; (2) the field testified to must be of a state of the art that such an expert’s testimony could be sufficiently reliable; (3) the witness must have sufficient expertise to offer the intended testimony.”  DeHanes v. Rothman, 158 N.J. 90, 100 (1999) (quoting State v. Kelly, 97 N.J. 178, 208 (1984)).

It is important to remember that trial judges are responsible to act as gatekeepers for the purpose of excluding unreliable expert testimony.   This typically involves an analysis by the trial court as to whether the expert’s theory or technique has been tested objectively.  Expert testimony which is found to be merely subjective or conclusory should be held inadmissible because its reliability cannot be assessed. The trial court will also want to know whether the expert’s data or research has been published and subjected to peer review. The trial court may also wish to know the known rate of error of the technique or theory when applied.  The expert’s theory or technique should not be based on arbitrary information but should be supported by standards and controls which have been tested and are generally accepted in the scientific community. If a witness lacks the requisite qualifications of an expert, it may serve as a basis for a motion in limine to bar the expert’s testimony.[6]  In the alternative, this information may be useful for voir dire and cross-examination of the purported expert.


Cross-examination of an expert is often a crucial element in determining the accuracy, reliability, and probative value of the expert’s findings and opinions. To determine the credibility, weight, and probative value of an expert’s opinion, the practitioner must question the facts and reasoning on which it is based.  What has the expert relied upon and where did he get the facts and data in order to render his opinion? Practitioners should consider obtaining the expert’s notes and communications with the attorney who has retained the expert.[7]  New Jersey discovery rules and procedures are “liberally construed to compel production of all relevant, unprivileged information which may lead to the discovery of relevant evidence.” Franklin v. Milner, 150 N.J. Super. 456, 465 (App. Div. 1977).  With regard to communications between the attorney and their expert, this evidence is only protected under the attorney work product privilege where such disclosure would reveal the “mental impressions, conclusions, opinions, or legal theories of an attorney.” R. 4:10-2(c).   However, where the attorney has provided facts and data considered by the expert in rendering the report, the communications are not protected by the attorney work product privilege and are fair game in discovery under R. 4:10-2(d)(1).[8]

If it can be demonstrated to the trial court that the facts upon which the expert has relied are faulty, then the expert’s opinion can be challenged as faulty.  Sometimes the expert will rely upon information provided by the trial attorney, but if the expert has not taken any steps to independently verify this information, the expert’s testimony may be impeached.  On occasion, experts rely on research, articles, and learned treatises which may form the bases for their opinion.  In preparation for trial, each and every one of these materials should be reviewed in order to determine whether the research cited categorically supports the opinion of the expert and whether the research has been criticized in professional quarters.

Do not forget that experts are not fact witnesses. In that regard, they may rely on hearsay and other information not admissible in evidence if that expert would reasonably rely on those kinds of facts and data in forming an opinion on the subject. N.J.R.E. 703; Blanks v. Murphy, 268 N.J. Super. 152, 163-164 (App. Div. 1993).  For example, in a custody evaluation, the expert may rely on statements made by relatives and friends which may otherwise be considered hearsay if they are presented in court by a fact witness.  If third-party sources have made statements that the expert has reasonably relied upon in his report, you should consider taking the deposition of these third-party witnesses in order to ascertain their credibility and the veracity of any statements which were made to the expert.

Finally, you must also be mindful of N.J.R.E. 703 which provides that the expert’s opinion must be based on the facts or data.  The corollary to this rule is an expert that offers an opinion not based on facts or evidence has rendered a “net opinion.”  Courts will bar opinions made without support of any factual evidence or data, textbook treatise, standard custom recognized practice, or anything other than the personal view of the expert, unfounded speculation and unquantified possibilities.  Townsend v. Pierre, 221 N.J. 36 (2015). Put another way, the expert must “give the why and wherefore that supports the opinion, rather than mere conclusion.”  Borough of Saddle River v. 66 E. Allendale, LLC, 216 N.J. 115, 144 (2013).  The family law practitioner should move to bar an expert from testifying when his report lacks evidentiary support and is a “net opinion.”


Upon receiving the expert’s report, consideration must be given as to whether it is prudent strategy to depose the adverse expert before trial. R. 5:3-3(f). If the expert is deposed, will that assist in locking in his testimony at trial and obtaining concessions on important points?  Or, will proceeding with a deposition tip off the adverse expert to your trial strategy and questions that may have otherwise been posed for the first time during cross-examination at trial?  The deposition may also alert the adverse expert of the need to correct deficiencies in his report.  In the end, the determination of whether to depose the expert must be made on a case by case basis.[9]


After all relevant documentation and information about the adverse expert has been obtained in the course of discovery, the practitioner must then decide how to best utilize it at trial.  Although there are a number of avenues in which the qualifications and opinions of an expert can be challenged effectively, it is up to counsel to develop a plan for cross-examination.  An effective cross-examination of the adverse expert will present a theme to the trial judge as to why the expert’s opinion is not credible and should not be relied upon.  Perhaps the expert is honest but mistaken, or purposely exaggerating or shading his testimony, or even relying on faulty factual information.  The possible reasons for why an expert’s testimony may not be reliable are virtually limitless.

In some instances, experts may attempt to testify about issues or subjects which are either inconsistent with or go beyond the scope of their report.  Skibinski v. Smith, 206 N.J. Super. 349 (App. Div. 1985).  A trial court has the discretion to exclude expert testimony that deviates from the pretrial expert report if the court finds “the presence of surprise and prejudice to the objecting party.”  Velazquez ex rel. Velazquez v. Portadin, 321 N.J. Super. 558, 576 (App. Div. 1999), rev’d on other grounds, 163 N.J. 677 (2000).  “It is well settled that a trial judge has the discretion to preclude expert testimony on a subject not covered in the written reports furnished in discovery.” Ratner v. General Motors Corp., 241 N.J. Super. 197, 202 (App. Div. 1990).  To properly evaluate whether parts of an expert’s testimony must be stricken based on testimony about subjects and issues outside the purview of their report, the court must consider the following: “(1) the absence of a design to mislead; (2) absence of the element of surprise if the evidence is admitted; and (3) absence of prejudice which would result from the admission of the evidence.”  Westphal v. Guarino, 163 N.J. Super. 139, 145-146 (App. Div.), aff’d, 78 N.J. 308 (1978). [10]

Experts may also make statements at trial which are contradictory to testimony which they may have given at a deposition or other proceeding.  Under N.J.R.E. 613(b), extrinsic evidence of a prior inconsistent statement, such as a deposition transcript, may be introduced after the witness is afforded an opportunity to explain or deny the statement.  Prior inconsistent statements may be used not only for impeachment purposes, but also for substantive value provided that the witness is available for cross-examination.  State v. Gross, 121 N.J. 1 (1990); State v. Hacker, 177 N.J. Super. 533, 537 n. 2 (App. Div. 1981), certif. denied, 87 N.J. 364 (1981).

Other forms of extrinsic evidence which may come into play to cross-examine the adverse expert are prior reports of the expert in other cases on the same subject. Similarly, published works by the adverse expert which undermine the opinions rendered in his present report can be used on cross-examination. To find out whether the expert has published contradictory works or issued reports at odds with his present position, the practitioner should review the expert’s website to see what materials may be posted and speak with colleagues who have had prior experiences with the expert.

Finally, counsel must consider the question of whether the adverse expert’s report should be admitted into evidence.  While parts of an expert’s report used for impeachment purposes on cross-examination may be admitted, an expert’s report generally is not admissible since it is hearsay falling under no exception enumerated in N.J.R.E. 803. Corcoran v. Sears Roebuck & Co., 312 N.J. Super. 117, 126 (App. Div. 1998).  Practitioners should object to an adversary attempting to admit into evidence an expert report, especially when it is intended to bolster the inadequate trial testimony of the expert.  Having said the above, it is not uncommon for family law attorneys to consent to admit into evidence the expert reports from both sides as it may be of assistance to the trial judge. Little Egg Harbor Twp. v. Bonsangue, 316 N.J. Super. 271, 280 (App. Div. 1998).  Before agreeing to such an exchange, keep in mind some experts write their reports better than others, while some experts do not testify as well as their reports are written.  In the end, the family law attorney will have to decide if it helps or hurts the case to have all reports come into evidence.[11]


It cannot be emphasized enough that it is unlikely that you will completely “destroy” the adverse expert at trial. Experts are smart and will have far more experience in a particular subject matter than the trial attorney. Many experts appear regularly in the Family Part and come before the tribunal with an imprimatur of experience, competency and credibility. Therefore, it is imperative that counsel follow the cardinal rule of cross-examination and only ask leading questions requiring yes or no responses. N.J.R.E. 611 (c).  Open-ended questions will allow the expert to display their expertise on a subject, thereby helping to score points with the trial judge.

When cross-examining experts, focus on the area where the opinion is most vulnerable. Establish your point, and then move on.  In addition to boring the judge, a long cross-examination risks allowing the expert to rehabilitate himself by explaining away any inconsistencies and reconciling any areas of weakness in his testimony and report. Furthermore, the cross-examination should focus the court’s attention on the deficiencies you are looking to emphasize.  If the cross-examination is confusing or unclear, the attorney risks burying the most important points in the questioning.  If the cross-examination is not tight and becomes meandering, don’t be surprised if the trial court exercises its discretion to permit the expert to answer freely and to not be harnessed by the usual restrictions under the Rules of Evidence.

Finally, a copy of the transcript of the direct examination of the adverse expert should be obtained when possible, especially if there are significant breaks in trial days.  That transcript may assist you in impeaching the expert on cross-examination if the expert attempts to deviate from his direct testimony. Be prepared to address a particular issue that comes up on direct examination that may not have been anticipated in preparing for trial.  What you learn during direct examination may serve as the impetus for revising or supplementing your cross-examination.


The cross-examination of an expert witness is one of the hardest skills for a family law attorney to master.  While areas of cross-examination will vary from case to case based on the type of expert who is testifying and the issues which are in dispute, there is no substitute for preparation.  Following the ten steps outlined in this article will put you in the position of being able to successfully cross-examine an adverse expert at trial.

* John P. Paone, Jr. is a Diplomate of the American College of Family Trial Lawyers; an Editor Emeritus of the New Jersey Family Lawyer; and managing partner of the Law Offices of Paone, Zaleski & Murphy located in Red Bank and Woodbridge.  John P. Paone, III is a senior associate at the firm.

[1] The Appellate Division recently made clear that expert analysis can be relied upon in the determination of the marital lifestyle in alimony cases.  S.W. v. G.M., 462 N.J. Super. 522 (App. Div. 2020).

[2] It is well settled that failure to furnish names of witnesses to be used at trial may result in the sanction of excluding the witnesses from testifying.  Burke v. Central Railroad Co. of N.J., 42 N.J. Super. 387, 394-95 (App. Div. 1956).

[3] “The court at trial may exclude the testimony of a treating physician or of any other expert whose report is not furnished pursuant to R. 4:17-4(a) to the party demanding the same.”  R. 4:23-5(b). On the other hand, an expert witness may testify without providing a report where no request for a report was made. Kiss v. Jacob, 268 N.J. Super. 235, 241 (App. Div. 1993).

[4] See Levine v. Wiss & Co., 97 N.J. 242 (1984) holding that accountants jointly selected by the parties can be held liable for negligence. In making this holding, the New Jersey Supreme Court observed that “there is no special significance to be attached to the fact that the (experts) were appointed by the parties pursuant to court order.”

[5] See Franklin v. Milner, 150 N.J. Super. 456 (App. Div. 1977). While discovery from the consulting expert is prohibited absent a showing of “exceptional circumstances,” discovery from a testifying expert can be had as to all communications between attorney and expert regarding the facts and data considered by the expert in rendering the report. R. 4:10-2(d)(1).

[6] Practitioners should be aware of the new rule concerning motions in limine. R. 4:25-8 which went into effect September 1, 2020, would preclude a motion in limine to bar an expert’s testimony if such action would have a dispositive impact on a litigant’s case.  In such cases, practitioners should be filing a summary judgment motion in connection with moving to bar an expert’s testimony.

[7] Generally, all preliminary or draft reports are deemed trial preparation materials and are not discoverable under R. 4:10-2(d)(1).

[8] Be mindful that in addition to the work product privilege, the attorney-client privilege may also be claimed with the expert acting as the agent of the attorney to whom confidential information has been imparted.  The attorney-client privilege has been held to extend to third parties whose advice is necessary to the legal representation. O’Boyle v. Borough of Longport, 218 N.J. 168 (2014)

[9]  A completely different analysis on deposing the adverse expert must be made when an adverse party elects to withdraw or to not proceed with an expert previously identified to be called at trial. Fitzgerald v. Stanley Roberts, Inc., 186 N.J. 286 (2006).

[10] Practitioners will also have to decide whether to move to sequester expert witnesses at the commencement of trial. Expert witnesses are subject to sequestration in the same manner as lay witnesses. State v. Lanzel, 253 N.J. Super. 168 (Law Div. 1991). N.J.R.E. 615 gives the court the discretion of sequestration and makes no exception for expert witnesses. Most courts will not sequester expert witnesses as, unlike fact witnesses, expert testimony is constrained by the contents of the expert’s report. State v. Popovich, 405 N.J. Super. 324 (App. Div. 2009

[11] Under R. 5:3-3(g), the report by an “expert appointed by the court may be entered into evidence upon the court’s own motion or the motion of any party in a manner consistent with the Rules of Evidence.”  Also, some reports may be admissible at trial under the “business records exception” to the hearsay rule if they were prepared and maintained in the ordinary course of business by a forensic expert, were made within a short period of time of the events described in it, and the trustworthiness of the report is undisputed.  N.J.R.E. 803(c)(6); State v. Kuropchak, 221 N.J. 368, 388 (2015); State v. Matulewicz, 101 N.J. 27, 29 (1985) (citation omitted).  New Jersey Division of Child Protection and Permanency (DCP&P) reports are admissible in custody cases under the business records exception.  R. 5:12-4(d).