Using Pre-Trial Hearings and Discovery to Set the Stage for Persuasive Use of Experts at Trial


Despite the fact that experts have always played a prominent role in both civil and criminal trials, many lawyers have failed to challenge experts utilized by the prosecution. This is despite the fact that some so-called "experts" were unqualified, poorly trained, lazy, or testified beyond their expertise. Some simply fabricated testimony. In many instances, we, as criminal defense lawyers, have failed to challenge substandard laboratories and "science" that is not truly science at all.

We have often fallen far short of taking full advantage of the opportunity we have as defense attorneys to obtain experts to provide us the education we need to effectively cross-examine and challenge prosecution experts, and we have missed opportunities to use our own experts in the proactive defense of our clients.

We must master the Rules of Evidence and prevailing case law so that we can employ the most effective strategies to properly deal with expert testimony. We cannot concede the qualifications, or the conclusions, of expert witnesses, and we must make our decisions within the context of the themes and theories central to the litigation. We also need to practice thinking "outside of the box" and employ creativity as we work with our experts to destroy those employed by the prosecution at every possible opportunity.


The practitioner must have a working knowledge of the Rules of Evidence in your jurisdiction. For purposes of this discussion, we will rely on the Federal Rules of Evidence, since many State evidence rules are substantially the same as the Federal Rules or otherwise model theirs upon them.

First, we will discuss Federal Rules of Evidence 702-705 relating to expert testimony.


If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.

FRE 702 provides that a person who is qualified by knowledge, skill, experience, training or education, may offer testimony of a scientific, technical, or specialized nature if it will assist the trier of fact in those areas. The expert can, but does not have to, offer an opinion; if an opinion is offered, it must be based upon sufficient data and be reliable both in its principles and methodology. In addition, since the December 2000 amendments to the Rule delineating the three prerequisites for admissibility, there are numerous objections available to the defense attorney related to challenging the reliability and the relevance of expert testimony.

Relevancy objections focus on the requirement that the testimony be helpful or assist the trier of fact, as evidence will be deemed inadmissible if the testimony reaches conclusions or draws inferences that are "within the jury's competence or within the exclusive function of the jury." Nichols v. American Nat. Ins. Co., 154 F.3d 875 (8th Cir. 1998).


The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to the expert at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence in order for the opinion or inference to be admitted. Facts or data that are otherwise inadmissible shall not be disclosed to the jury by the proponent of the opinion or inference unless the court determines that their probative value in assisting the jury to evaluate the expert's opinion substantially outweighs their prejudicial effect.

FRE 703 provides that an expert can rely on otherwise inadmissible evidence, if the inadmissible information is of the type "reasonably relied upon" by other experts in the field. For example, simply because an expert is relying, in part or in whole, upon hearsay information, an expert opinion is not to be excluded if the hearsay relied upon is the sort of information normally relied upon in the field of expertise. With respect to that inadmissible information, the rule does not permit the proponent of the expert opinion to reveal that information unless the court performs a FRE 403 type analysis and permits that information in. In such circumstances, the other side should seek a limiting instruction that informs the jury that the hearsay is not being offered for the truth of the matter asserted, but simply to illustrate the basis of the opinion. Of course, if the cross-examiner is interested in the jury knowing the nature of the underlying hearsay, he has the right to inquire at his own risk.


(a) Except as provided in subdivision (b), testimony in the form of an opinion or an inference otherwise admissible is not objectionable because it embraces an ultimate issue to be decided by the trier of fact.

(b) No expert witness testifying with respect to the mental state or condition of a defendant in a criminal case may state an opinion or an inference as to whether the defendant did or did not have the mental state or condition constituting an element of the crime charged or of a defense thereto. Such ultimate issues are matters for the trier of the fact alone.

FRE 704 differs from many State courts in which the opposite is true - that is, in many States, an expert cannot opine as to an ultimate issue except as it relates to the defense of insanity. Rule 704, however, allows experts to offer opinions and conclusions that may involve ultimate issues, except in the areas of the defendant's mental state if it regards an element of the crime. For example, an expert cannot testify as to whether a defendant had the requisite intent to commit an offense.


The expert may testify in terms of opinion or inference and give reasons therefor without first testifying to the underlying facts or data, unless the court requires otherwise. The expert may in any event be required to disclose the underlying facts or data on cross-examination.

FRE 705 obviates the need for an expert's opinion to be based upon a hypothetical question that divulges the entire factual foundation of the opinion and gives the expert leeway, subject to court approval, to offer an opinion without specifying the data it is based upon. The rule leaves to opposing counsel the role of bringing out the underlying data, obviously focusing on that data that undercuts the expert's opinion. However, the court retains discretion to require the expert, on direct examination, to disclose any admissible underlying facts or data the expert utilized or relied upon in forming the opinion.

The following are other evidentiary rules that interplay with those above:


Questions of admissibility generally. Preliminary questions concerning the qualification of a person to be a witness, the existence of a privilege, or the admissibility of evidence shall be determined by the court, subject to the provisions of subdivision (b). In making its determination it is not bound by the rules of evidence except those with respect to privileges.

FRE 104 (a) is an under-utilized, but powerful, tool for the criminal defense practitioner. It requires the court to allow an attorney to challenge the qualifications of an expert and the admissibility of his opinion, outside the presence of the jury. This would, of course, include Daubert/Frye challenges whereby the attorney can obtain a hearing and a ruling with respect to how Daubert/Frye applies to a particular expert or his proposed testimony. Rule 104(a) allows challenges to the qualifications of the expert before or during the trial and outside the presence of the jury. This type of voir dire examination during trial can be a very powerful tool, especially in circumstances where the qualifications are particularly suspect. In those situations, a choice may be made to voir dire the witness in front of the jury in advance of the direct testimony.


When a hearsay statement, or a statement defined in Rule 801(d)(2)(C), (D), or (E), has been admitted in evidence, the credibility of the declarant may be attacked, and if attacked may be supported, by any evidence which would be admissible for those purposes if declarant had testified as a witness. Evidence of a statement or conduct by the declarant at any time, inconsistent with the declarant's hearsay statement, is not subject to any requirement that the declarant may have been afforded an opportunity to deny or explain. If the party against whom a hearsay statement has been admitted calls the declarant as a witness, the party is entitled to examine the declarant on the statement as if under cross-examination.

Rule 806 is a powerful but under-utilized evidentiary rule, one offering the practitioner a mechanism for challenging hearsay statements when the declarant is unavailable. As mentioned a moment ago in our discussion of FRE 703, experts offering testimony routinely rely upon reports and information received from others.

Rule 806 can be utilized in a variety of contexts. For example, it can be used to attack an expert's decision to rely upon a lab report despite a determination that the lab was substandard, a test invalid, or a technician unqualified. Similarly, an expert may have based his opinion, in part, on information given by a person convicted of a crime (impeachable under Rule 609), or a bad act (impeachable under Rule 608) or who has given inconsistent statements.

Rule 806 needs to be a fixture in the practitioner's arsenal and used to attack hearsay statements used or relied upon by experts and lay witnesses alike. As an example of how the rule relates to non-experts, if a witness testifies to statements made to him by a co-conspirator during the course of, or in furtherance of a conspiracy under Rule 801(d)(2)(e), Rule 806 allows the defense practitioner to attack the non-testifying declarant or co-conspirator just as if he had given those statements on the witness stand.


To the extent called to the attention of an expert witness upon cross-examination or relied upon by the expert witness in direct examination, statements contained in published treatises, periodicals, or pamphlets on a subject of history, medicine, or other science or art, established as a reliable authority by the testimony or admission of the witness or by other expert testimony or by judicial notice. If admitted, the statements may be read into evidence but may not be received as exhibits.

FRE 803 (18), if it is utilized correctly, has the potential to enable an attorney to effectively call a witness (that could cost many thousands of dollars) without ever calling him to the witness stand; the witness could even be dead. Previously published work that qualify as a "learned treatise" can be acknowledged by your expert or the prosecution's expert and thus be used to undercut the opposing expert's opinion at trial. A previously published work acknowledged as a learned treatise can be utilized to support the testimony of your expert or to impeach the testimony of the prosecution expert. This is particularly effective if the prosecution's expert has testified to facts contrary to what is stated in a learned treatise authored by someone that expert (or our expert) has acknowledged as authoritative in the field. Note, however, that while excerpts can be read to the jury in cross, they cannot be admitted as substantive evidence.

In a child sex case I went to meet with one of our experts. In her office I noticed on her shelf a book on interrogation techniques of child witnesses. I had the same book at my office and ended up utilizing over 25 pages to bolster her testimony by a leading expert in the field. (Investigative Interviews of Children, (Lamb and Poole), American Psychological Association, Washington D.C. 1998).

In that same case we filed a Taint motion asserting that the then five-year old child's testimony was inadmissible under Rule 602 since her memory had been irrevocably compromised due to the leading and suggestive discussions of both family members and the Child services expert with the child. We asked for a pre-trial Taint hearing under rule 104. There was almost no Alabama law on the subject. To make sure the Court took it seriously as a valid Motion to Suppress, we filed a supplemental motion supported by case specific facts and law. (See Ex. 1). The judge afforded us an all day hearing without even a lunch break.

As an aside it is worth mentioning that Rules 401-402 still serve as the underlying benchmarks with regard to relevancy and probative value in determining the admissibility and scope of expert testimony as it applies to all of the above rules of evidence.


The criminal law practitioner will want to study pertinent cases that illustrate the application of those Federal Rules of Evidence applicable to expert testimony. At a very minimum, practitioners will want to be thoroughly familiar with Daubert V Merrell Dow Pharmaceuticals 509 U. S. 579 (1993), Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999) and Frye v. United States, 293 F. 1013 (D.C. Cir. 1923). Also important are the recent cases of Crawford v. Washington, 541 U.S. 36 (2004), and Davis v. Washington, 547 U.S. 813, 126 S. Ct. 2266 (2006), which should be read in the context of, and with an eye toward, effectively attacking expert testimony.

In Daubert the Supreme Court of the United States addressed FRE 702. The Supreme Court in Daubert held that if expert scientific testimony is proffered (often via Rule 104(a)), the trial court must determine if the expert will testify on a scientific matter that will aid the fact finder regarding a fact at issue. Thus, the Supreme Court made the trial court a gatekeeper as to the admissibility of such evidence. The standard the trial court must utilize is "...whether the reasoning or methodology underlying the testimony is scientifically valid," and "whether that reasoning and methodology properly can be applied to the facts in issue." Daubert at 592-593.

The court in Daubert listed five factors, although not exclusive, to more or less serve as a checklist to the analysis:

(1) whether the expert's technique or theory can be or has been tested---that is, whether the expert's theory can be challenged in some objective sense, or whether it is instead simply a subjective, conclusory approach that cannot reasonably be assessed for reliability;

(2) whether the technique or theory has been subject to peer review and publication;

(3) the known or potential rate of error of the technique or theory when applied;

(4) the existence and maintenance of standards and controls; and

(5) whether the technique or theory has been generally accepted in the scientific community.

Kumho is a case decided by the United States Supreme Court which expanded Daubert. The court in Kumho clarified that the trial court's gate keeping function to encompass not just scientific evidence, which formed the basis of the Daubert decision, but also expert testimony which is technical or otherwise. In other words, while the court in Daubert limited its discussion to the scientific expert testimony which was the issue of contention in that case, the court in Kumho expanded the analysis to include all other types of expert testimony. The Court recognized that some of the Daubert factors may not apply in all cases of expert testimony. However it encourages judges to use those factors where they apply, and otherwise gives the trial court broad discretion in making admissibility determinations- so long as the Court takes into account the concerns of reliability and relevance.

Before Crawford, the admissibility of expert testimony hinged on the application of State law with little concern for Sixth Amendment confrontation analysis, provided that the defendant was afforded an opportunity to cross-examine the expert witness. Such experts often were allowed to testify to hearsay provided to, and relied upon, by them. The Crawford decision and that of Davis v. Washington, may have dramatically changed this analysis. The United States Supreme Court in Crawford wrestled with the intersection of hearsay testimony and the Sixth Amendment.

The Davis Court attempted to refine what constitutes a testimonial statement in the context of 911 calls and crime scene statements made to law enforcement. The opinion, authored by Justice Scalia, held that "where testimonial evidence is at issue, [however], the Sixth Amendment demands what the common-law required: unavailability and a prior opportunity for cross-examination". Crawford v. Washington at 68. Rather than defining "testimonial", the court offered three types of testimonial statements, recognizing that these were not exhaustive:

1. Ex parte, in-court testimony or its functional equivalent, such as affidavits, custodial examinations, or prior testimony that a defendant had no opportunity to cross-examine, or other similar pre-trial statements that declarants would reasonably expect to be used prosecutorially.

2. Extra-judicial statements contained in formalized testimonial materials such as affidavits, depositions, prior testimony, and confessions, and

3. Statements that were made under circumstances which would lead an objective witness reasonably to believe that the statement would be available for use at a later trial.

In Davis, the court shifted its emphasis to the primary purpose of the interrogator rather than the declarant's understanding or purpose, which had been the focus in Crawford.

In most cases involving expert testimony, there is no interrogation. However, Justice Scalia did not limit the definition of testimonial to the context of interrogation. In the wake of Crawford, state courts are split on the question of whether lab reports (toxicology, autopsy, etc...) are testimonial and whether the business records exception to the hearsay rule support their admission. Despite what your state courts have ruled, it is important nevertheless to scrutinize all lab reports, medical reports, and any other purported business or public records, and object vigorously to any testimonial statements on the ground that their admission is a Sixth Amendment violation.

The United States Supreme Court has recent addressed but not fully answered the issue of whether these sorts of lab reports are admissible in whole or in part without the opportunity to cross-examine the maker of the report. (See Bullcoming v. New Mexico, 131 S. Ct. 2705 (2011)). In that case the Court, affirming its holding in Melendez-Diaz v. Massachusetts (129 S. Ct.2705 (2011)) reversed the New Mexico Supreme court and found a 6th amendment violation when the State offered a surrogate lab technician who did not participate in the testing to testify about it anyway.

In Bullcoming, Justice Sotomayor's dissent leaves open the scope of the ruling; in other words would she have voted the same way if the witness offered had real involvement in or supervised the testing? (See The Champion, October 2011 Crawford in the Lab-The Next Step: Bullcoming v. New Mexico).

Prosecutors will often argue that the objectionable parts of a business record or public record should be admitted because they are not being offered for their truthfulness, and thus, are not hearsay. Even when the prosecution, in a context other than a business or public record offers hearsay, they often argue that it is admissible because it is not offered for its truthfulness. The prosecutors in People v. Goldstein, 843 N.E. 2d 727 (2005), made that very argument; it was unsuccessful and repudiated by the New York Court of Appeals.

In Goldstein, the State's psychiatrist, over objection, was allowed to testify to hearsay statements made by Goldstein to third parties to support his opinion that Goldstein was not insane. The prosecutors argued that these third-party statements were not hearsay because they were not admitted for their truthfulness. The New York Court of Appeals ripped this argument into pieces acknowledging that the State's psychiatrist accepted what the third-parties said as true; if he had not, he would not have considered their statements in supporting his opinion. The court held that the Confrontation Clause did not allow the psychiatrist to recount third-party hearsay testimony without giving the defendant an opportunity to cross-examine each third party whose testimony was presented. Because that opportunity was not provided the defendant, reversible error occurred.

It is also worth noting that Rule 806 could have been utilized if the defense had discovered impeaching information affecting the credibility of those third-party lay witnesses, including prior convictions under Rule 609, and inconsistent statements or bad acts under Rule 608.

In a federal death penalty case we filed a motion to exclude the scope of the government's mental health expert due to the inadmissible hearsay contained within her report. The court excluded nearly 2/3rds of her proposed testimony and that motion may have saved our client's life. (Ex. 2)

Crawford/Davis objections should also be considered regarding the contents of any reports, including, but not limited to, medical reports, DNA reports, lab reports, and scientific reports of any type that reflect the opinions of, or information from, other individuals or sources

Prosecutors utilize expert-like testimony in a considerable number of trials. For example, prosecutors for many years (often without following the notice requirements of Rule 16) have called case agents to offer "summary testimony" to bolster their cases. See, e.g., United States v. King, 616 F.2d 1034, 1041(8th Cir. 1980), citing United States v. Esser, 520 F.2d 213 (7th Cir. 1975). This type of expert testimony may be inadmissible as an improper application of FRE 702, or inadmissible as a result of Crawford, and subject to being successful challenge. The good news is that Federal Courts are trending towards precluding or at least limiting Government agents from outlining the prosecution's case and offering "expert testimony" in this manner. See United States v. Griffin, 324 F. 3d 330 (5th Cir. 2003).

Other examples of the prosecution using Government agents as "expert witnesses," include agents testimony on such matters as the activities of drug dealers, gang members, tax and security fraud, and bank fraud, just to name a few. This is in addition to the experts that are routinely used by the Government, such as handwriting experts, pathologists, fiber experts, DNA, serology and toxicology experts etc.... On the other hand, criminal defense lawyers call experts to the stand in a relatively small number of cases.

We must become creative in our strategies as they relate to proactively utilizing expert testimony. For example, the Ninth Circuit, in United States v. Morales, 108 F.3d 1031 (9th Cir. 1997), reviewed the Defendant's conviction for wrongfully making false entries in a Union ledger in violation of Federal statutes. The Defendant proffered an expert to show that he lacked requisite bookkeeping knowledge relevant to the question of mens rea. While the defendant was not successful in that case, the Ninth Circuit did find, however, such expert testimony to be relevant and proper under Rule 702.

In a competency hearing on a federal death penalty case, the government filed a Daubert motion to exclude one of our experts, an attorney with expertise in the area of death penalty litigation and competency issues. The court denied the governments motion and allowed our attorney-expert to testify in that hearing on the issue of our client's competency. (see Ex.3, our response to the government's motion).

One underutilized area for the criminal defense lawyer to utilize expert testimony is in the area of sentencing and during sentencing hearings. For example, we recently concluded a case where a former pharmacy employee embezzled almost $400,000.00. We retained the services of a forensic psychologist who offered testimony to mitigate the commission of the crime. Specifically, the psychologist testified at the sentencing hearing not only to the remorse exhibited by the client but also that the client was experiencing a major depressive episode during the time period in which the theft occurred and the underlying reasons for the depression.

The psychologist had a plausible explanation for the conduct, while not excusing it, influenced the judge to sentence our client to only 6 months of confinement and four months of unmonitored home detention. The minimum guideline range was 27-33 months. The judge, however, considered the psychological report and testimony in his analysis of the factors called for by 3553(a) in formulating what was a very favorable sentence in light of the seriousness of the offense.

Similarly, in another federal sentencing, our client had stolen 1.1 million dollars from her employer over a several year period. We offered the testimony of a psychologist to testify that our bi-polar client suffered severe from long term but untreated depression. The court substantially departed from the minimum guidelines and granted a variance, resulting in a favorable sentence consistent with what we suggested in our sentencing memorandum. (Ex. 4, our sentencing memo).

In an 841 drug distribution case, the government recommended a 50% reduction to a sentence of 23 months. But the normally guideline following Federal District Judge appropriately varied under Section 3553 (a) and sentenced him to sixty days in a county jail, followed by home confinement due to a previous Traumatic Brain Injury (TBA). The medical submissions convinced the Judge that at the time of the crime, based upon the damage to his frontal lobes, his judgment was seriously impaired especially in light of his character and background. In addition the Judge believed that in a prison setting he would be "easy prey," and one hard hit to his head could prove fatal.


Choosing an appropriate expert can be a challenge. At my firm, we attempt to select an expert that someone we trust has used that expert before. Internet search engines, list-serves, and websites provide more information than ever before to help us make the best expert choices. Searching through Lexis or Westlaw for reported cases in which your potential expert has previously testified is also very important. Google and social media can be very useful. NACDL also provides many resources to locate and aid in the investigation of experts in almost every field.

If your client is indigent, or indigent for purposes other than attorneys' fees, file a motion to proceed ex parte (See Ex. 5) and then a separate motion for funds, citing Ake v. Oklahoma, 470 U.S. 68 (1985.) Keep in mind that The United States Supreme Court and the Sixth Amendment right to the effective assistance of counsel trump any limitations found in state statutes, legislation and case law.

Even if you are retained by the family of your client, if he is indigent and has no control over the payment of the fees, you are still entitled to expenses. In that case you need to file a Motion to Declare the Defendant Indigent for Purposes Other than Attorney Fees setting out that your client is both indigent and has no control over the payment of your attorney fees. (See Ex. 6). However, unless a particularized motion with supporting affidavits is made showing the critical need for the requested expert and funds, appellate courts will not reverse a trial judge for failure to provide the same. (See Ex. 7).

Such motions must be made ex parte and under seal with a request for an ex parte hearing. It is crucial that you know and articulate your working theories and that you clearly state the need for the expert, as well as the expected fees that the expert will charge. You should state in your motion that if the money is exhausted, you will return to make a further showing of the need for additional funds. (See Ex. 8). Denial of a critical expert is a denial not only of the Sixth Amendment right to the effective assistance of counsel for your client, but also may very well deny your client the right to present a defense. Chambers v. Mississippi, 410 U.S. 284 (1973); see also Mark J. Mahoney, The Right to Present a Defense, (1989-2009).

Your expert can also help you attack Government expert testimony, as well as refine your theories of defense. In a DUI homicide we defended, our nineteen-year old client drove the vehicle which crashed killing two of his friends and seriously injuring another friend and himself. The State charged him with two counts of murder and as serious assault count.

In an effort to obtain youthful treatment and probation for him we employed the following experts:

  • A Neuro-psychologist (he had a TBI and total amnesia re event)
  • A Psychologist to treat him for depression and PTSD
  • A Psychiatrist to treat him with appropriate medications
  • An Alcohol and Drug specialist and counselor and expert in Alternative Sentencing
  • An Accident Reconstruction expert

After almost four years, the Judge granted him both YO status and probation, with stringent conditions, in spite of one of the family members who pushed for thirty years (See Ex. 9 YO letter to Court). We also convinced the DA to stipulate to the facts with him accepting our accident reconstruction expert's conclusions re speed. In addition we utilized the expert services of a Neuro-psychologist, substance abuse expert and family counselor. (See Ex.10- Proposed Stipulation of Facts)

Caution - do not let your expert roam free. Keep in close touch as many will go off on tangents or develop their own theories that may work in the scientific world but not in the world of law.


In addition to personally speaking with other attorneys who have used the expert, and reviewing reported cases where the expert is mentioned, check out any advertisements, CV's, and websites, as well as articles authored by the expert. It is not just the prosecution's experts that exaggerate and fabricate; many individuals that offer their services as expert witnesses allow financial considerations to override their integrity, and many have weaknesses in their background that must be considered.

For example, Terrica Redfield, the NACDL Death Penalty Resource Director, and I happened to be in a courtroom in a small town in Alabama waiting to speak to the prosecutor about a capital murder case we were defending. We watched in horror as a defense psychologist was being cross-examined by the prosecutor on the issues of mental retardation and mitigation. The prosecutor adeptly brought out previous testimony of the expert from another trial that the expert was not at all prepared to confront. The prosecutor was also able to emphasize that this expert's proficiency was in sexual discrimination and eating disorders and that she had never been trained in the mitigation area, nor did she possess any particularized expertise in the area of mental retardation. The jury rejected her testimony with hardly a thought.

In another capital murder case, the defense, to combat the State's DNA expert, called a very qualified DNA expert that they had retained. However, at the end of cross-examination of the defendant's expert, the prosecutor showed DNA images to the expert. When pressed, the defense DNA expert was forced to support the State's DNA expert that it was, in fact, probably the Defendant's DNA.

The point, of course, is that retaining and presenting an expert in a criminal case is not a matter to be taken lightly. We have to conduct thorough research before making our choices, and sometimes it may be best to use your expert to help you prepare an attack on the prosecution's expert rather than calling him to testify.


Successfully attacking a prosecution expert is a goal within the reach of any prepared trial lawyer. The methods discussed to choose your expert are the similar to the ones used to investigate your own experts.

The following, though far from being exhaustive, are some basic suggestions to consider:

1. Use the Internet to investigate the prosecution's expert.

As stated above, search engines, including Google, offer extensive information on the background and history of experts.

2. Find lawyers who have used/faced the expert before.

3. Use Westlaw, Lexis, or other legal resources, including NACDL, to locate other cases in which the expert previously testified and/or lawyers who are familiar with the expert.

Sometimes courts have criticized experts in reported opinions and reported opinions reveal the names of lawyers who have confronted these experts before.

4. Obtain the expert's CV and check the validity of its contents.

Many experts are simply not qualified in the respective fields in which they testify. Many exaggerate their qualifications, including their education. Some testify in areas well beyond their expertise. Many simply lie on their CV; some never even attended the schools they list. Some even lie about their publications or contributed little, if any, to the ones they list.

5. Research through the advertisements and the websites of the prosecution's experts.

If there ever is a place to exaggerate, it is in an advertisement; many experts exaggerate when they advertise.

6. Obtain all writings of the expert.

Experts, especially those in the academic field, have written on a variety of subjects. Sometimes these experts forget what they have written many years ago, or even just one or two years previously. Some experts contribute very little to publications that they pretend to take credit for when they list their qualifications.

7. Obtain the past testimony or transcripts of the expert.

Experts that have faced cross-examination have probably testified in ways that they may later regret. Many will testify inconsistently in one case to the way the same expert will testify in yours. If nothing else, you will get a true flavor for the way they present themselves as revealed in transcripts, and talking to the lawyers who have examined these experts will fill in the gaps.

8. Subpoena all underlying raw data the experts relied upon. (see Ex. 11- but the motion should be specific for all every scrap of paper, including emails, handwritten notes, validations, control tests etc. and manuals can be separately subpoenaed).

The raw data includes lab notes, reports of others, emails, validation results, and any information that they were aware of, considered, or reviewed, prior to any testing they conducted or at the time at which they offered their opinions.

9. Research any of the labs that the experts are associated with.

Many labs are unaccredited or have been cited numerous times by government oversight agencies or private watchdogs. This can lead to very fertile cross-examination.

10. Interview the prosecution's expert in person whenever possible.

Many of the prosecution's experts are supposed to be neutral. Forensic experts who are employees of the State are supposed to work for the people, not just the prosecution. Most would be willing to meet with you. This will allow you to assess the expert as well as many of the opinions he or she is expected to make.

In many cases I have met with forensic pathologists and reviewed the case with them. Then I know what I may need my own pathologist (see Ex. 11) to explore, and all that aids my future cross examination of the state's expert.

11. Subpoena any and all laboratory procedures manuals.

Many forensic lab scientists are lazy and sometimes do not follow their own procedures; some may not even be aware of them.

12. Expose any hidden bias on the part of the expert.

In a recent case we learned that a prosecution expert gives the Government a fee break. We also learned that a Federal Judge, years before, had written an opinion questioning the credibility of this same expert. At a hearing, he was so flabbergasted to be confronted with the transcript and Opinion, he called the respected Federal Judge (also from our State) "pompous, hard headed and just plain wrong".

Many of the prosecution's forensic experts are obviously biased. This bias can be simply because they work so closely with the prosecutors and only testify for them. It can be from personal relationships formed with the prosecutors or police. The bias can result from correspondence sent by the police or prosecutors which includes prejudicial information. It is for this reason that we need to consider a defense expert to consult with and/or call as a witness to crucial crime scene testimony that is in dispute including but not limited to areas within the realm of a forensic pathologist. (See Ex's. 12, 13). Often good ones once worked for the State.

For example, U.S. citizen and an attorney, Brandon Mayfield was labeled a material witness after his fingerprints were supposedly found on a bag full of detonating devices associated with the bombing of a train in Madrid on March 11th, 2004, in which 191 people were killed and 2,000 others were wounded. In spite of the fact that Spanish forensic experts believed that the FBI considered an insufficient number of points of comparison before declaring a "match", the FBI arrested and detained Mayfield on the basis of the fingerprint comparison. In fact, Mayfield was a Muslim convert who had helped defend a person accused of attempting to travel to Pakistan to support the Taliban. Mayfield was subsequently completely cleared when it was determined that the fingerprints actually belonged to an Algerian.

13. Use learned treatises in preparation of your cross-examination of the Government's expert.

As previously mentioned, portions of learned treatises (803(18)), if adopted by either expert, can be very powerful. If the state's expert is expected to contradict a learned treatise, preparation is the key to exposing the weakness of the testimony.

14. When possible, make their expert confirm significant portions of your case and your theories.

In 1998, we represented a client charged with capital murder in the Northern District of Alabama. In cross-examination of the Government's psychologist during the sentencing phase, we were able to force her to confirm each and every mitigating factor that our expert testified to. In addition, she was forced to admit that our expert had many more qualifications than she did. (See previous Ex. 2).

Like every witness, expert witnesses have weaknesses and vulnerabilities. Investigating the expert and the subject matter will provide opportunities to not only level the playing field, but to also gain an advantage. The science may be vulnerable; the expert may have credibility gaps, and the bias may be exposable - almost any expert witness is vulnerable to attack or neutralization.

It is also important to remember that experts, like many professionals, often have big egos. Perhaps the expert's ego is greater than the basis of his or her opinion. It would be difficult to find an expert without some weak areas. It could be simply that the expert is testifying to matters beyond his expertise or offering opinions not adequately supported by the facts. The prepared trial lawyer, who demonstrates early on knowledge of the subject matter and the vulnerabilities of the expert, opens the door to an exciting opportunity to control and destroy the expert.

The fear of embarrassment and humiliation is a concern for many witnesses - but even more so with experts. It is important to remember, however, that many experts have been trained in the presentation of testimony, and that instills confidence in them. Nonetheless, a prepared and tenacious lawyer, with developed cross-examination skills, still has the advantage because the courtroom is his home. The expert is a visitor and if he is your adversary, he is an intruder.

15. Insist that the prosecution follow Rule 16.

Prosecutors sometimes disclose limited information regarding their experts. In fact, Rule 16(g) requires the Government to give a written summary of any expected testimony under Rule 702, 703 and 705 if it plans to call that expert in its case-in-chief. The summary must describe "...the witness' opinions, the basis and reasons for those opinions and the witness' qualifications".

We need to vigorously hold the prosecution's feet to the fire as it relates to complying with Rule 16(f), (g), by writing letters and filing motions and, when necessary, litigating their non-compliance with the Rule.


There exists an ever expanding opportunity to challenge traditionally accepted expert opinions because, as technology evolves, new and improved methods of analysis become available everyday. As a result, the processes upon which government witnesses have traditionally relied are becoming increasingly vulnerable to attack from the well-prepared and innovative litigator, and yesterdays accepted techniques may well become tomorrow's junk science.

There are already examples out there of creative litigators using newly discovered scientific and technological advancements to challenge traditionally accepted expert opinions, such as in the areas of handwriting (U.S. v. Saelee, 162 F. Supp. 2d 1097) or bullet lead analysis (U.S. v. Mikos, 2003 WL 22922197 (N.D.Ill.)). But perhaps more instructive for those who seek not only to take advantage of existing changes in the law but to forge new paths on behalf of our clients, is the example of Robert Epstein.

Mr. Epstein took on the formidable task of challenging the long-established science behind fingerprint identification in his efforts to defend a bank robbery case he was assigned as a federal defender in Philadelphia, PA. His approach and determination in attacking this sacred cow of forensic science should serve as a guide to any of us that wish to navigate uncharted waters in our efforts to provide our clients the best defense possible.

Mr. Epstein maintained that, while testimony about the nature of ridges, arches and points of comparison were obviously admissible, an ultimate opinion stating that a certain number of points of comparison were sufficient to identify a partial latent print as belonging to one person to the exclusion of all others in the world went beyond the acceptable bounds of scientific certainty required by Daubert. Mr. Epstein's challenges to fingerprint evidence led the National Institute of Justice to release a request for certain data, namely data that would establish the validity and standardization of friction ridge analysis...the very kinds of data required by Daubert, and the data that the NIJ had claimed was unavailable.

Though his struggles did not lead to the exclusion of the evidence at question, Epstein's efforts, both in his creative identification of an area ripe for challenge and his dogged pursuit of information through the post trial proceedings, (which led to further evidence of a knowledge on the part of the FBI that such standardized information on fingerprint comparison was not available) can serve as a guide for each of us as we prepare to present a credible case to a judge as to why the same evidence he has admitted a hundred times before might, in the light of new information, be inadmissible.

And how do we prepare to present that credible case? First, we must fully understand the area of scientific knowledge we are seeking to challenge, especially those portions that are most vulnerable when scrutinized in light of Daubert and newly available techniques which may have cast a new and critical light on previously accepted science. Kim Kruglick's fantastic resource page at is an excellent jumping off point for the practitioner looking to better understand the nuances of a particular subject.

With apologies to Al Franken, this heading seems perfect for a subject that deserves at least passing mention. Some experts lie. They aren't mistaken. They don't misinterpret the information given to them, they simply make up the data and conclusions necessary to help their side prevail. Obviously, it behooves the defense counsel to identify and expose these liars at every opportunity, because they pose an ongoing threat not only to our clients, but to the credibility of the court system we are sworn to uphold.

FBI crime lab technician Katherine Lundy, and indeed the entire FBI crime lab, have been found to have offered false testimony. Crime Labs in Florida, Arizona and Texas also caused false testimony to be offered against criminal defendants. It is a problem that must be reckoned with through diligence and determination.

An awareness of the past problems is crucial to identifying potential laboratory fraud, which is why every criminal defense practitioner should regularly check the following two sites:

and They provide a running commentary on most instances of laboratory fraud, and understanding the methods used by these discredited experts will better prepare us to spot potential fraud in our own cases.

It is important that lawyers proactively litigate issues in regard to experts through pre-trial motions and hearings. And it is just as crucial that lawyers use experts creatively, actively and aggressively on behalf of their clients.

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