In order for a medical opinion to be admissible as evidence in civil, criminal and administrative cases, the basis of the opinion must fulfill either the Daubert[1] Criteria or the Frye[2] test, depending on the jurisdiction. The judge of the court rules on the admissibility of the expert opinion.  The effect of Daubert has been to limit expert testimony to opinions which are based on a scientific foundation. Daubert specifies that adequate scientific support and method and a known error rate must exist. The testimony of a mental health expert rendering an opinion using criteria which does not meet Daubert standards is weakened by the implication that it is not based on “sound science.” In some instances, for example, a mental health expert uses an approach where there are no peer-reviewed studies or methods, such as when psychologists compose their own neuropsychological test batteries. In most cases where an attorney is considering a “Daubert challenge,” a contemporaneous and up-to-date literature search is indicated. Also, extensive case law presently exists as to specific issues. Being familiar with the Daubert criteria enhances effectiveness in challenging a mental health expert’s opinion, whether on voir dire or cross examination. On direct examination, the strengths of an opinion reached under Daubert criteria become a “teaching moment” for the trier of fact, because it will be founded on the science of mental health assessment.

Rule 702 of the Federal Rules of Evidence, Testimony by Expert Witnesses, states that

“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 better prepared the psychiatric consultant, the better will be his testimony.  When the conclusions and the logic are well understood, jurors are most likely to find themselves in agreement with the expert’s opinions and rationale. Conversely, the better prepared the attorney is for the opposing expert’s cross-examination, the more fruitful the cross-examination will be.

The above seems face obvious but is worth mentioning because of its importance. As an expert, I believe it is my job to educate the attorney for whom I work about psychiatric pathology, its relevance to the case and how the attorney can elicit the best evidence from me and the best evidence from the opposing expert. I do not believe a psychiatrist helping an attorney prepare direct or cross-examination question is advocacy. It is the expert’s job, I believe, to educate the attorney so that the attorney can help the expert educate the jury or other Trier of Fact about the matters the expert is expert at. If the expert understands the litigation process to be one of discovery, then assisting an attorney to discover contradictions or deficits in the opinion of an opposing expert is not advocacy, but rather Expert Witnessing once removed. Furthermore, it is necessary for the expert to understand the basis of the opinions reached by the opposing expert in order to fully consider the basis of his opinion.


As a general background, in Daubert v. Merrell Dow Pharmaceuticals, Inc.[3], the U.S. Supreme Court held that the Frye[4] “general acceptance” test was superseded by adoption in the Federal Rules of Evidence and that admission of scientific testimony is governed by Federal Rule of Evidence 702. In short, the Daubert criteria requires that the expert’s opinion be reached by use of “scientific methodology,” essentially formulating hypotheses and conducting experiments to prove or falsify the hypothesis. To establish the validity of the conclusion it is necessary to use empirical testing, that the method be (or has been) subjected to peer review and publication, and that it have a known or potential error rate. Further there must exist maintained standards and controls concerning the operation of that method (e.g. for example how a psychological test is administered, scored, tested and interpreted). Validity is further established by the degree to which the theory and technique is generally accepted by a relevant scientific community.


With the adoption of Daubert, the court defined “scientific methodology” as the process of formulating hypotheses and then conducting an experiment(s) to prove or disprove (falsify) the hypothesis. To be admissible, a theory or technique must be falsifiable, refutable and testable. Also, it must be peer reviewed, published, and have a known or potential error rate. There must be the existence and maintenance of standards and controls concerning its operations. The theory and technique is generally accepted by the relevant scientific community. The testimony is based on sufficient facts or data. The testimony is the product of reliable principles and methods. And, the witness has applied the principles and methods reliably to the facts of the case.

The American Psychological Association then addressed the Daubert ruling within the context of psychological testing and expressed four (4) guidelines to apply to Daubert.

1. Use theoretically and psychometrically adequate data gathering instruments.

2. Draw conclusions using scientifically validated theoretical positions.

3. Weigh and qualify testimony on the basis of the adequacy of theory and empirical research on the questions being addressed.

4. Be prepared to defend the scientific status of your data gathering methods during the process of qualifications as an Expert Witness.

The Frye Test is the alternative basis for the court permitting an expert opinion to be admitted into evidence.  The Frye Test is applicable in certain jurisdictions. Admissibility of scientific evidence under Frye states novel scientific evidence is admissible if it has “gained general acceptance in the particular field in which it belongs.” The Court keeps pseudo-science out of evidence by deferring to those in the field.


A line of questioning I have suggested to attorneys regarding “reasonable medical probability” of a medical opinion is the degree of certainty expressed by the expert based upon all of the evidence reviewed. This line of questioning will tend to uncover whether or not an expert is biased for the side he is testifying for and whether the expert has considered contradictory testimony. In order for a medical opinion to be admissible in a civil court, criminal court or other legal venue, the conclusion must be reached with a “reasonable medical probability” or “reasonable medical certainty” which means the opinion is “more likely than not” true. In most contested cases, there may be a “battle of the experts” whereby contradictory opinions are expressed based upon the same evidence which is weighed differently by the various experts. If an expert has an opinion of which he is only 51% certain, then this must mean that there is 49% of contradictory data available which had to be countered. It is worth exploring which of the data is contradictory to the expert’s opinion; doing so may reflect a bias or sufficient consideration of medical evidence which does not support his opinion. Inquiry may also reveal a lack of understanding by the expert about what constitutes an admissible medical opinion. Many experts do not understand the legal basis for expressing a medical opinion. Instead, they believe that if a medical condition is “possible” then they can testify to it as a medical opinion. They also do not understand the Daubert Criteria (or the Kelly/Frye Criteria in applicable jurisdictions) and thus are not able to forensically weigh the medical evidence. On cross examination, revealing this ignorance in the expert is clearly beneficial. Also, revealing the expert’s ignorance about these guidelines may enable the attorney to have the expert’s opinion disregarded or rejected by the court as not being applicable, relevant or admissible.


The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition generally is accepted as the standard for identifying the necessary clinical criteria for various psychiatric disorders. In November 1995, the American Journal of Psychiatry, Volume 152 Supplement, provided detailed guidelines for an adult psychiatric evaluation titled “Practice Guidelines for Psychiatric Evaluation of Adults.” A sufficient mental status examination is the equivalent of a physical examination by a “regular doctor,” i.e., non-mental health professional. The Mental Status Exam is a description of the various mental functionings or their manifestation at the time the examination is conducted. In my opinion, the mental status examination should include the following elements:

• General appearance including dress, gait, posture, facial expression, cooperativeness, accessibility, alertness, tenseness, restlessness, friendliness, tidiness, disorderedness, broodiness, agitation, negativism, indifference, stupor, or stereotypic behavior.

• General activities such as normal compulsive bizarre or retarded movements, pressured activity, hand wringing, pacing or crying.

• Disorders in speech such as scanning, hesitating, slurring or stuttering as well as an inability to identify objects.

• Disorders of thinking such as whether the thinking is interrupted. Thought production including flow of thought, acceleration or retardation and distractibility. Thought continuity such as clearness of thought, coherence, relevance, whether the thoughts ramble, whether they are not specific to the topic at hand, whether or not perseveration occurs i.e., the individual stays on the same topic even though the examiner moves to another topic, flight of ideas whereby the examinee’s ideas flit from topic to topic without completion, or blocking, whereby thoughts are not completed.

• Thought content includes the evaluee’s formation of concepts, handling of ideas, anxieties, fears, obsession, phobias, hypochondriacal preoccupations, body image concerns, autistic thinking, ideas of reference or ideas of influence (paranoid type thinking), self-depreciation, suicidal ideas, somatic delusions, other systematized delusions, self-referential thinking, hallucinations (abnormal sensory experiences), apprehensive expectation (anticipating bad things happening), fears of abandonment or feelings of estrangement.

• Emotional state should indicate how well emotions are regulated, mood swings, control of emotions, anxieties, feelings of unreality, perplexity, agitation, irritability, depression, apathy, elation, restlessness, or emotional numbing.

• Somatic functioning can include headaches, pains, or other medical system abnormalities. This can include but is not limited to disturbances of sleep, eating, appetite, weight, bowel regularity, sex, alcohol or drug abuse, or excessive smoking.

• Mental grasp should be assessed regarding the person’s understanding of his or her current situation, attention, concentration, memory, ability to calculate, engage in abstract reasoning and the quality of their judgment. An absence of an adequate mental status assessment may constitute a defective psychiatric or psychological evaluation and permit a challenge as to the adequacy of the expert’s opinion.


In my opinion, the best psychological personality test available for assessing personality organization is the Minnesota Multiphasic Personality Inventory 2, better known as the MMPI-2. This is the most widely given psychological test in the world. It is the best studied test and the test most agreed upon between inter-rater assessment i.e., two separate specialists looking at the same test results would agree with the interpretation of the test. As a psychiatrist who has administered at least 2,000 MMPI-2s, been trained in its use and who has qualified as an expert on the MMPI-2 in multiple jurisdictions, I believe that the use of the test is justified and helpful. The MMPI-2 is accepted under Daubert and Frye.

The MCMI-III, the Millon Clinical Multiaxial Inventory-III, is in my opinion not a particularly useful test in a forensic setting because it overdiagnoses personality disorders. I believe the test may not fulfill the Daubert Criteria either, in that only three questions out of 175 questions address the test taker’s attitude. The judge ruling on admissibility may rule it does not have a falsifiability rate that is scientifically reliable.

Many tests are face obvious. This is not a reason to avoid them, but it does impact their reliability.


There exist many peer-reviewed neuropsychological test batteries which assess various parameters of cognitive functioning. Those include but are not limited to the Halstead-Reitan Battery, the Luria-Nebraska Test Battery, the WAIS-III Battery, the Wechsler Memory Scale III, the Wisconsin Card Sort, Trails A and B and about a thousand others.

Some neuropsychologists use nonstandard procedures, that is to say they administer parts of various test batteries in order to perform a forensic assessment of an individual’s neuropsychological functioning. I believe that under Daubert, this may not be admissible because the nonstandard procedures are not falsifiable and they have not been peer-reviewed. This flexible battery approach, therefore, has not been subjected to adequate scientific testing. Whereas clinically the use of parts of tests are widely accepted by the psychological community (thus fulfilling the Frye criteria) it may not fulfill Daubert).  Even if the examiner is qualified to administer these tests, I believe Daubert opens the door to challenge the admission of this neuropsychological evidence in a medical-legal setting. There is a distinction between methodology and qualifications. Said another way, Daubert requires that in order for an expert’s opinion to be admissible, the entire reasoning process must be valid. A link must exist between the test results and the conclusions drawn.


Forced-choice testing means the test taker must provide an answer to a question. This type of testing is one way to assess reliability.


The MMPI-2 has multiple validity scales. Low scores of recognition in the California Verbal Learning Test is also suggestive of diminished reliability as are the Memory Assessment Scales. Atypical performance on tests such as the Wechsler Memory Scale revised or the WAIS-III may raise questions of reliability.

When cross-examining a neuropsychologist about the neuropsychological assessment of an allegedly brain-damaged individual, I believe the absence of forced-choice testing greatly undermines the reliability of the proffered opinion. Given the medical-legal context of a neuropsychological injury, I believe it is incumbent upon the neuropsychologist to use forced-choice testing. As a psychiatrist who is often involved in neuropsychiatric cases, I myself often administer forced-choice tests as part of my mental status examination.


In light of the above, I believe it is worth repeating the key to testimony by an Expert Witness:

Rule 702 of the Federal Rules of Evidence, Testimony by Expert Witnesses, states that

“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.)”

[1] Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 113 S. Ct. 2786, 125 L. Ed. 2d 469 (1993)

[2] Frye vs. United States 293 F. 1013 (DC Cir 1923)

[3] Op. Cit.

[4] Op. Cit.