In the United States, we talk of the requirements for admissibility of expert witness opinion testimony; proffered testimony must be relevant and reliable. If the requirements go unsatisfied, the legal consequence is usually limited to the preclusion of the expert witness’s challenged opinion. If the opinion is necessary to support the sponsoring party’s claim or defense, the further legal consequence may be the entry of judgment adverse to the retaining party.
A few states have permitted a party to sue its own expert witness for “expert malpractice,” committed in the scope of the witness’s engagement as an expert witness. See, e.g., LLMD of Michigan Inc. v. Jackson-Cross Co., 740 A.2d 186 (Pa. 1991). Fewer states permit the adverse party to sue its adversary’s expert witness. Davis v. Wallace, 565 S.E.2d 386 (W. Va. 2002).
In the United Kingdom and Canada, courts impose duties directly upon expert witnesses themselves. The following enumeration is frequently cited as setting forth the independent duties, owed to the court, by expert witnesses:
“1. Expert evidence presented to the Court should be, and should be seen to be, the independent product of the expert uninfluenced as to form or content by the exigencies of litigation.
2. An expert witness should provide independent assistance to the Court by way of objective unbiased opinion in relation to matters within his expertise. An expert witness in the High Court should never assume the role of an advocate.)
3. An expert witness should state the facts or assumption upon which his opinion is based. He should not omit to consider material facts which could detract from his concluded opinion.
4. An expert witness should make it clear when a particular question or issue falls outside his expertise.
5. If an expert’s opinion is not properly researched because he considers that insufficient data is available, then this must be stated with an indication that the opinion is no more than a provisional one. In cases where an expert witness who has prepared a report could not assert that the report contained the truth, the whole truth and nothing but the truth without some qualification, that qualification should be stated in the report.
6. If, after exchange of reports, an expert witness changes his view on a material matter having read the other side’s expert’s report or for any other reason, such change of view should be communicated (through legal representatives) to the other side without delay and when appropriate to the Court.
7. Where expert evidence refers to photographs, plans, calculations, analyses, measurements, survey reports or other similar documents, these must be provided to the opposite party at the same time as the exchange of reports.”
National Justice Compania Naviera S.A. v. Prudential Assurance Co. Ltd., (“The Ikarian Reefer”),  2 Lloyd’s Rep. 68 at 81-82 (Q.B.D.), rev’d on other grounds  1 Lloyd’s Rep. 455 at 496 (C.A.)(embracing the enumeration of duties).
It is unclear, however, what the consequences of breach of these duties are. Often the sponsoring party may be complicit in the breach, and the harm will be to the court and the adverse party.
In the United States, perhaps the heavy lifting of judicial gatekeeping, required by Federal Rule of Evidence 702, might be assisted in recognizing these independent duties of expert witnesses.
The duties of expert witnesses, set out in the The Ikarian Reefer, have been generally accepted by courts in Ontario and throughout Canada. See, e.g., Frazer v. Haukioja, 2008 CanLII 42207, at ¶141 (O.S.C.) (Moore, J.) (quoting from Ikarian Reefer). The Ontario court system decided not to leave compliance with these duties to chance or instructions from counsel. Starting in 2010, Ontario’s New Rule 4.1 of its Rules of Civil Procedure went into effect to define explicitly the duties of an expert witness:
RULE 4.1 DUTY OF EXPERT
It is the duty of every expert engaged by or on behalf of a party to provide evidence in relation to a proceeding under these rules,
(a) to provide opinion evidence that is fair, objective and non-partisan;
(b) to provide opinion evidence that is related only to matters that are within the expert’s area of expertise; and
(c) to provide such additional assistance as the court may reasonably require to determine a matter in issue.
The duty stated in the Ontario Rule 4.1 trumps any contractual or positional obligations expert witnesses may owe to the parties that engaged them. Remarkably, the Ontario courts do not leave to chance whether expert witnesses will understand and act upon their mandated obligations. Ontario Rule 53, subrule 53.03(2.1), requires expert witnesses to submit signed acknowledgment forms (Form 53, below), which recite their understand of their duties.
Courts of Justice Act
ACKNOWLEDGMENT OF EXPERT’S DUTY
1. My name is _______________________________ (name). I live at
___________________ (address), in the __________________ (name of city) of _________________________ (name of province/state).
2. I have been engaged by or on behalf of ___________________ (name of party/parties) to provide evidence in relation to the above-noted court proceeding.
3. I acknowledge that it is my duty to provide evidence in relation to this proceeding as follows:
a. To provide opinion evidence that is fair, objective and non-partisan;
b. To provide opinion evidence that is related only to matters that are within my area of expertise; and
c. To provide such additional assistance as the court may reasonably require, to determine a matter in issue.
4. I acknowledge that the duty referred to above prevails over any obligation which I may owe to any party by whom or on whose behalf I am engaged.
Date: ___________________ ___________________________ (signature)