The Expert Witness as Gun, Gunfighter, and Gatekeeper

Author: admin
Date: 09.06.2020 Time to read: 12 min

“Observation and perception are two separate things; the eye that observes is stronger, the eye that perceives is weaker.” -- Miyamoto Musashi


The “hired gun” reputation that follows expert witnesses will never die. The lawyer views the expert witness as a gun to fire at his discretion. The judge views expert testimony warily, unsure if to even let the testimony step foot into court town. And the expert witness is a gunfighter balancing demands from lawyer employer, rules of “sheriff” judge, and the evidentiary bullets from the opposing side’s gunfighter. All in the hopes of winning the duel in the eyes of the jury townsfolk. Ultimately, the hired gun’s only loyalty is to just that --- the gun. And that is how it should be.


That lawyer psychology predisposes itself to gunfighting is close to reality; after all, juries saddle expert witnesses with the ‘hired gun,’ stereotype. And to a lawyer, the expert witness is a literal gunfighter to be aimed at the lawyer’s discretion.


Daubert accidentally addressed the problem

Daubert is an analyses zombie. Every time an analysis strips what we all thought was the last edifying piece of flesh on the carcass, Daubert returns, ready for another fleecing. I know that you know what Daubert is, but formalities are what they are, so…Daubert established a “reliability” test comprised of several non-all-inclusive factors that a court must consider when ruling on the admissibility of expert witness testimony.

The need to take the admissibility of expert testimony away from judicial discretion highlights the nature of expert testimony: it’s special. And powerful. Daubert stands for the proposition of judge as gatekeeper of all expert witness testimony. However, Daubert’s intent was for a more lax standard than the Frye standard. The Supreme Court of the United States through Daubert opined that its goal was to allow a broader range of expert witness testimony into open court. Justice Blackmun even noted that so long as an expert’s scientific testimony rests upon ‘good grounds’ . . . it should be tested by the adversarial process.

Daubert is an analyses zombie. Every time an analysis strips what we all thought was the last edifying piece of flesh on the carcass, Daubert returns


Yet, the opposite state of affairs obtains today. Daubert is the stricter standard. Civil defendants successfully took control of the narrative. The idea that junk science was extremely prejudicial flourished. So the viewpoint of  Daubert morphed into that of keeping pseudo-science out of the courtroom, rather than broadening the types of admissible expert testimony.

Regardless, the gatekeeping function within the context of Daubert has and continues to have its day. But the rules of evidence make the expert witness a gatekeeper of evidence as well as an advocate. Analyzing these functions of the expert witness clarifies Daubert and why courts have viewed Daubert as calling for tight control over the admissibility of expert witness testimony.

Where these powers inhere

The Expert Witness is the personification of a reasoning process that while valid is alien to a juror’s mind. The juror can choose to accept the expert witnesses reasoning process and the resulting inference or ignore it.

Rule 702 sketches what the court views an expert as:

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:

(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;

(b) the testimony is based on sufficient facts or data;

(c) the testimony is the product of reliable principles and methods; and

(d) the expert has reliably applied the principles and methods to the facts of the case.

The court recognizes that the expert has specialized knowledge in (a). Merriam Webster’s sense (1)(c) of knowledge is “the circumstance or condition of apprehending truth or fact through reasoning.” This sense ostensibly applies to the expert witness, who has acquired his knowledge through a reasoning process. Philosophically, knowledge has the same meaning and defines “reasoning process.” Reliablism posits that a process that reliably produces true beliefs withstands scrutiny as a “reasoning process.”

Consequently, an expert witness has used a specialized reasoning process to arrive at a conclusion using the particular facts of the case.

The expert witness mirrors the courtroom in that way. A court uses a specialized reasoning process to come to a conclusion regarding the total evidence in a case. This analogy is useful to understand the next set of rules.

Rule 703 outlines the contours of an expert’s testimony:

An expert may base an opinion on facts or data in the case that the expert has been made aware of or personally observed. If experts in the particular field would reasonably rely on those kinds of facts or data in forming an opinion on the subject, they need not be admissible for the opinion to be admitted. But if the facts or data would otherwise be inadmissible, the proponent of the opinion may disclose them to the jury only if their probative value in helping the jury evaluate the opinion substantially outweighs their prejudicial effect.

Accordingly, the expert witness can use his judgment to pick out what types of evidence to rely on for his opinion. This evidence itself can be admitted with a limiting instruction if it passes a balancing test. The court, in recognizing that the expert witness uses a reasonable process, assumes that the evidence the expert witness utilizes are necessary and useful to that process. Of course this deference finds limit when it comes to admitting the evidence itself into open court. Only when that evidence, according to the judge, is so vital to understanding the expert witness’s testimony that the court can exempt it from the normal prejudice guards in the rules of evidence, can the court admit it.

The Expert Witness is the personification of a reasoning process that while valid is alien to a juror’s mind.


Rule 704 tells us what the expert witness may opine on:

In General — Not Automatically Objectionable. An opinion is not objectionable just because it embraces an ultimate issue.

Exception. In a criminal case, an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense. Those matters are for the trier of fact alone.

The expert witness may directly opine on the ultimate issue of fact in a civil and criminal trial. The only exception is in a criminal trial, where the court prohibits an expert witness from testifying regarding a criminal defendant’s mental state. Rule 704 essentially grants the expert witness the capacity to state out loud an opinion that a jury could or would make in a trial.

The rationale here is that an expert witness himself represents a reasoning process, and accordingly, because his opinion necessarily is rational (or presumed to be so), the court may allow his opinion on the ultimate issue of fact. The comments to the rule clarify that indeed, the expert witness functions as a juror’s thought process (and that this was a matter of some debate for many years).

The older cases often contained strictures against allowing witnesses to express opinions upon ultimate issues, as a particular aspect of the rule against opinions. The rule was unduly restrictive, difficult of application, and generally served only to deprive the trier of fact of useful information. 7 Wigmore §§1920, 1921; McCormick §12. The basis usually assigned for the rule, to prevent the witness from “usurping the province of the jury,” is aptly characterized as “empty rhetoric.” 7 Wigmore §1920, p. 17.


Many modern decisions illustrate the trend to abandon the rule completely.

These provisions afford ample assurances against the admission of opinions which would merely tell the jury what result to reach, somewhat in the manner of the oath-helpers of an earlier day. They also stand ready to exclude opinions phrased in terms of inadequately explored legal criteria. Thus the question, “Did T have capacity to make a will?” would be excluded, while the question, “Did T have sufficient mental capacity to know the nature and extent of his property and the natural objects of his bounty and to formulate a rational scheme of distribution?” would be allowed. McCormick §12.

The debate obstensibly settled in favor of the expert witness. Between rule 703 and 704, the expert witness serves as a gatekeeper --- like a judge --- and rational inference giver --- like a jury. This latitude enables him to pursue his reasoning process unfettered by normal courtroom procedure. His specialized knowledge essentially can stamp somewhat inferior evidence with the seal of “reason,” making it fit for inclusion in an opinion. The rationale here is that because the expert witness represents a reasoning process, then he is a reasoning process that can rationally make use of the evidence given. And so, by serving as a proof-of-concept, represents a special case for normally deficient evidence to have sufficient probative value and relevance for reasonable consideration.

The “battle of the experts” is modern litigation. And this battle highlights the expert witness in another role: the quasi-advocate.



Rule 705 and comments cement this logic into the law:

Unless the court orders otherwise, an expert may state an opinion — and give the reasons for it — without first testifying to the underlying facts or data. But the expert may be required to disclose those facts or data on cross-examination.

The hypothetical question has been the target of a great deal of criticism as encouraging partisan bias, affording an opportunity for summing up in the middle of the case, and as complex and time consuming. Ladd, Expert Testimony, 5 Vand.L.Rev. 414, 426–427 (1952). While the rule allows counsel to make disclosure of the underlying facts or data as a preliminary to the giving of an expert opinion, if he chooses, the instances in which he is required to do so are reduced. This is true whether the expert bases his opinion on data furnished him at secondhand or observed by him at firsthand.

If the objection is made that leaving it to the cross-examiner to bring out the supporting data is essentially unfair, the answer is that he is under no compulsion to bring out any facts or data except those unfavorable to the opinion. The answer assumes that the cross-examiner has the advance knowledge which is essential for effective cross-examination. This advance knowledge has been afforded, though imperfectly, by the traditional foundation requirement. Rule 26(b)(4) of the Rules of Civil Procedure, as revised, provides for substantial discovery in this area, obviating in large measure the obstacles which have been raised in some instances to discovery of findings, underlying data, and even the identity of the experts.

The rule allows expert witnesses to testify as to the ultimate issue and state the reasons for their opinion. However, it allows the expert witness to withhold the specific facts and data leading to that opinion. It is up to cross-examining counsel to ferret out which facts and data, unfavorable to the opinion, that the expert witness either discounted or ignored. This of course opens the door to counsel bringing forward all the facts and data --- favorable --- on re-direct, because the earlier balancing test under 703 now has the additional weight of “completeness” in counsel’s favor. Rule 705 essentially allows the unrestricted admission of inferences regarding facts in open court. The court gives the expert witness such deference because of the foregoing discussion and only limits that deference to the court unquestionably admitting facts that are inadmissible.

Expert witness as quasi-judge and jury

The expert witness qua reasoning process may choose which evidence to admit into his or her analysis. And without doubt, the inferences that arise from this evidence will come out in court. As discussed, the court allows the expert witness such discretion because admission via expert testimony makes the inferences prima facie rational.

In this sense, the expert witness functions as the judge does, in admitting and considering only relevant and probative evidence for analysis. So, the judge, in admitting expert witness testimony, is essentially allowing a witness to admit snippets of any evidence he or she chooses (in the form inferences) into court.

Also, the expert witness analyzes both the weight and probative value of the evidence given to him to produce an opinion on the ultimate issue of fact --- which mirrors a juror’s intended process as well. These powers are awesome. Not unlike a sovereign granting quasi-sovereign status to a smaller entity: a deputy badge.

Further, expert testimony, due to its esoteric nature, is unlikely to find comprehension from either judge or jury. Consequently, the judge must take great care in admitting expert testimony because of the power courts give experts.

The judge may fall short of understanding the expert witness testimony, but the judge can assess other indicia of reliability --- as it would with any other piece of evidence. The expert witness, by holding him or herself out as an expert witness, takes on special obligations to the court regarding candor.

At Expertpays, we believe that expert witnesses are vital to the court battle. Never bring a knife to a gunfight.



Why Daubert unfolded in this way

Now Daubert fits well into the analysis. Daubert in intent assures the court that more fields than scientific fields and more methods than those that have wide acceptance are reasonable admissible processes. But Daubert in effect tightly focuses on whether the reasoning process meant to substitute for a juror’s own reasoning process is what it says it is. And Daubert instructs the court on how to assess this quality via indirect means (without comprehending the testimony itself).

  • Whether the theory or technique employed by the expert is generally accepted in the scientific community;
  • Whether it has been subjected to peer review and publication;
  • Whether it can be and has been tested;
  • Whether the known or potential rate of error is acceptable; and
  • Whether the research was conducted independent of the particular litigation or dependent on an intention to provide the proposed testimony

Notice that Rule 702 reflects this test (it was amended post-Daubert).

While the intent of Daubert – as stated --- was to lower the standard set before by Frye --- the effect has been the opposite. Plaintiffs have been thwarted in Daubert jurisdictions and often forum shop for Frye jurisdictions.

Civil defendants were able to control the narrative on Daubert precisely because of how powerful an expert witness’s testimony can be. The fear of “junk science” looms. Once it is in open court, it becomes difficult to strip it of that initial seal of court approval and credibility. Or so the thinking goes. The Supreme Court may have to clarify Daubert; petitions of certiorari to the Supreme Court have increasingly battled over Blackmun’s “good grounds” dicta.

This conflict was inevitable precisely because modern litigation makes use of ever more expert witness testimony. The “battle of the experts” is modern litigation. And this battle highlights the expert witness in another role: the quasi-advocate.

Ultimately, the hired gun’s only loyalty is to just that --- the gun. And that is how it should be.



Expert Witness as Quasi-Advocate

The court has feared the expert witness-as-advocate since the inception of expert witness testimony. Ethical rules against expert witnesses taking fees contingent on the outcome of a case exist for this reason. And the expert witness has additional powers that make for a powerful advocate. As we have seen from Rule 703, the expert witness may testify based on facts without direct knowledge of those facts. Any fact counsel has presented evidence for at trial, the expert witness can repeat in his or her testimony. Moreover, the presentation style can be at the expert witness’s choosing --- narrative, summation, chronology.

The power to get inferences out into open court serves a powerful advocacy role; and flowing from that, the ability to get inadmissible facts into open court, under limited circumstance and with a limiting instruction.

To a lawyer, the expert witness qua reasoning process is a means to an end. The process, a revolver, the evidence, silver bullets in the chambers, and the application of that reasoning process --- the bang from the hammer drop. All to take down the defense argument beast.

That lawyer psychology predisposes itself to gunfighting is close to reality; after all, juries saddle expert witnesses with the ‘hired gun,’ stereotype. And to a lawyer, the expert witness is a literal gunfighter to be aimed at the lawyer’s discretion.

Little surprise then, that the history of expert witness testimony until present day has had the dark cloud of “adversarial bias” over its head. The view of expert testimony contemporaneous with Daubert was dim. And, if anything, the pressures on expert witnesses to become partisan advocates has increased since Daubert.

The Expert Witness Advocates His Reasoning Process

Counsel and the expert witness are both advocates, but they are advocates with different aims. Counsel is bound only to zealous advocacy on behalf of the client. Counsel is unbound by any rule of reason.

The expert witness, if we accept that the expert witness is a reasoning process that a juror may either accept or reject, is an advocate only of his reasoning process. As such, the expert witness must demonstrate --- directly and indirectly --- that his work is reasonable and bound by reason.

Jurors give expert witnesses much less presumptive credit than many experts and lawyers believe. Most of them know that wide disagreement exists among experts within their respective fields. Jurors also dismiss weak conclusions and any appearance of confusion will turn the jury off of your testimony.

Jurors loathe jargon, so avoid using jargon. The jurors will thank you for it. Aim less for simplicity and more for clarity. Never be afraid to repeat yourself. So long as what you are saying is easy to repeat, you maximize your chances of being eventually being understood.

Convey your message is as many ways as possible: visual aids help. So do props.

The impression of knowledge matters most, here. Even the most complicated beyond-lay-thought explanation can leave the uninitiated awestruck. If it is said with confidence, if it is clear enough to repeat, and if it is repeated often, it will be remembered. And if it is remembered, it will eventually be either understood or at the very least, adopted.

At day’s end, sticking to your guns ensures you do right by the lawyer who retained you, the judge who qualified you, and the jury who placed their trust in you. The expert witness is meant to be a ‘hired gun,’ in this sense --- loyal to none but the reasoning process gun. The better the gun, the more likely a juror will want to use it for himself to decide the case.

At Expertpays, we believe that expert witnesses are vital to the court battle. Never bring a knife to a gunfight.


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