Using law enforcement experts in federal criminal cases

On October 6, 2008, the United States Court of Appeals for the Second Circuit in United States v. Mejia, 545 F.3d 179 (2d Cir. 2008),1 placed new limits on the use of law enforcement agents as experts in federal criminal cases. The court reversed the convictions of two young men accused of participating in drive-by shootings to enhance their positions within a street gang known as MS-13 or Mara Salvatrucha.2 The Second Circuit held that the testimony of a member of the task force investigating MS-13 as an “expert” in gangs violated the Federal Rules of Evidence and the defendants’ confrontation rights under Crawford v. Washington, 541 U.S. 36 (2004).3
This article discusses (1) the rise of the federal agent as expert gang witness; (2) the limits placed on the use of such experts by Mejia; and (3) the next area of litigation – discovery.
The Use of the Agents as Expert Witness on Gangs

The use of agents as expert witnesses in gang cases paralleled the federal prosecution of organized crime and narcotic trafficking cartels. Armed with enhanced statutes,4 the federal prosecutors began calling law enforcement officers as expert witnesses in organized crime cases in the 1980’s. Agents testified to “the nature and structure of organized crime families” as well as to terminology used in criminal activity such as narcotics trafficking.5 The use of gang experts expanded to street gangs, like Los Solidos6 and more recently, Mara Salvatrucha.

The Federal Rules of Evidence, Rule 702, permits witnesses to offer opinions as experts where the trial court finds that “scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue.” The court must find that the witness is qualified “by knowledge, skill, experience, training, or education” and that “(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.”
Courts have analogized the testimony of agents regarding gangs to that of anthropologists who use their education and fieldwork to form opinions on the cultural mores of a particular social group. Courts have found this similar to agents who use their experience and training to testify to the operation, symbols, jargon, and internal structure of criminal organizations.7

This analogy is flawed, however. Social science research is subjected to peer review in which individuals, often with contrary viewpoints, examine the basis and reasoning of the methodologies used and the opinions derived. In contrast, agents are generally searching for information which bolsters their cases. Their methodology and opinions are not objectively criticized. Rather, they are evaluated on how useful they are to the investigation and prosecution of particular cases. While ideally prosecutors and police are seeking truth and justice, our adversary system makes them partisans and advocates of their case.

FRE Rule 703 permits an “expert” to base an opinion on facts or data which is “reasonably relied upon by experts in the particular field in forming opinions.” Such facts or data need not be admissible in evidence and are not disclosed to the jury unless the court authorizes it. In the case of an agent witness, the opinion may be based on whatever law enforcement officers may use to reach an opinion – such as uncorroborated statements of informants or what is learned from other agents. Under FRE Rule 705, the witness may not be required to disclose the underlying facts or data until cross-examination.

As a result, the agent witnesses were permitted to testify to opinions drawn in some cases from the investigations which led to the indictment. The court in Mejia recognized the tendency of law enforcement officers, who often have a stake in the outcome of the case, to cross the line from providing legitimate expert opinion testimony regarding the structure and jargon of the group to substituting “expert opinion for factual evidence.” In such cases, the expert testimony can become central to the case, corroborating fact witnesses, providing missing information and synthesizing the trial evidence into “a coherent, discernible, internally consistent picture of the defendant’s guilt.” In such cases, the law enforcement officer, who is often the government’s case agent, is no longer assisting the jury, but substituting his or her own judgment for that of the jury.

The Limits Placed on the Use of Such Experts by Mejia

The Second Circuit has increasingly recognized that permitting such testimony must have limits to avoid abuse. In Mejia, the court said that the use of such testimony should be limited to “those issues where sociological knowledge is appropriate.” Although the Second Circuit began expressing its “discomfort” with such testimony more than 20 years ago, until lately it has been unwilling to upset convictions after finding that the error was “harmless.”8

The court finally held that the government went too far in Mejia. In that case, the government called as an expert witness a New York State investigator. Over the objections of trial counsel, the witness testified about the use of firearms, narcotics trafficking and multiple homicides allegedly conducted by members of MS-13 and aspects of the alleged gang’s operations, such as which alleged members attended meetings, the use of telephones to communicate and interstate travel to avoid prosecution or carry contraband. In addition, he summarized the activities of the anti-gang task force over several years including its investigation of dozens of homicides attributed to MS-13.
The court found that this testimony violated FRE 702 on several grounds. Much of it concerned material “well within the grasp” of the average juror. The court held that “Expert testimony might have been helpful in establishing the relationship between these facts and MS-13, but it was not helpful in establishing the facts themselves.” The court said that the government could not substitute expert testimony for factual evidence or use FRE 703 as a means to simply transmit hearsay evidence to the jury. The court also found that testimony regarding post arrest statements made by out of court declarants violated the defendant’s rights under Crawford.


Under Rule 16 of the Federal Rules of Criminal Procedure, a party must only disclose “a written summary of any testimony” and “describe the witness’s opinions, the bases and reasons for those opinions, and the witness’s qualifications.” Fed. R. Crim. P. 16(b)(1)(C). An expert in a criminal case is not required to present and disclose an expert report in advance of testimony. In comparison under the civil rules, a party must disclose an expert’s written report. That report must include not only “a complete statement of all opinions the witness will express and the basis and reasons for them,” Fed. R. Civ. P. 26(a)(2)(B)(i), and his qualifications, R. 26(a)(2)(B)(iv), but also all of the data or other information considered in forming the opinion, all summary or supporting exhibits, and the compensation he was paid. Id. R. 26(a)(2)(B)(ii)-(iii), (vi). Under the civil rules, an expert may be deposed. Under the criminal rules, depositions are only available to preserve testimony.

The emerging issue is what must a party disclose to satisfy its duty to provide “the bases and reasons” for the expert’s opinion. In U.S. v. Vasquez and Castro, the retrial of the prevailing appellants in Mejia, the government argued that it need only describe the types of materials underlying the opinions. Under their formulation, it would be sufficient to disclose that the expert relied on interviews with cooperating witnesses without disclosing the identities of the interviewees. The defense has moved to compel additional disclosure. The trial judge has not ruled at the time this article was prepared.

The government will continue to use federal agents as expert witnesses in criminal cases at every opportunity. Defense counsel must challenge these efforts to ensure that the trier of fact and not the government decides the innocence or guilt of the accused.

Peter J. Tomao, Esq. represents clients in criminal and civil cases before federal and state courts. He has more than thirty years experience before federal courts and is a former Assistant U.S. Attorney in the Eastern District of New York. He served as chairman of the Federal Courts Committee and as a director of the Nassau County Bar Association and is a past president of the Theodore Roosevelt American Inn of Courts. His offices are in Garden City.

1. The government intends to retry the case. The trial is scheduled for September 2009 before U.S. District Judge Arthur D. Spatt in Central Islip. The government has given notice that it again intends to call a law enforcement officer as an expert on gangs, albeit a different one.
2. What distinguished the case against these young men from that of others accused of street crimes is that the federal government brought the case under the statutes designed to attack racketeering enterprises. As a result, the defendants David Vasquez and Ledwin Castro received sentences ten times greater than the corresponding state sentences.
3. Recently the Second Circuit reversed the conviction of another defendant based on the testimony of the same “expert.” United States v. Rubi-Gonzalez, 2009 U.S. App. LEXIS 3797 (2d Cir. Feb. 25, 2009).
4. These acts include the Rackeeter Influenced and Corrupt Organizations Act, 18 U.S.C. §§ 1961-68 (“RICO”), and the more recently, the Violent Crimes in Aid of Racketeering Act, 18 U.S.C. § 1959.(“VICAR”).
5. In United States v. Ardito, 782 F.2d 358 (2d Cir. 1986), the Second Circuit approved the use of an FBI agent to testify as an expert about terms such as “captain,” “capo,” “regime” and “crew.” Id. at 363. The court reasoned that such testimony “aided the jury in its understanding of” recorded conversations between the two defendants. In cases like United States v. Levasseur, 816 F.2d 37, 45 (2d Cir. 1987), the Second Circuit permitted a law enforcement officer to offer expert testimony on the meaning of coded messages. In United States v. Daly, 842 F.2d 1380 (2d Cir. 1988), an FBI agent was permitted to describe the five organized crime families that operate in the New York area including their requirements for membership, their rules of conduct and code of silence, and the meaning of certain jargon. The agent had testified to “the existence of a RICO enterprise” specifically the Gambino crime family. See, also, United States v. Locascio, 6 F.3d 924, 936 (2d Cir. 1993) (upholding an FBI agent’s expert testimony about the internal operating rules of organized crime families, the meaning of recorded conversations, and the identification of members of the Gambino crime family). United States v. Matera, 489 F.3d 115, 121 (2d Cir. 2007) (upholding the admission of an officer’s expert testimony “about the composition and structure of New York organized crime families” and observing that the district court had limited the expert’s testimony to general information rather than information about the defendants themselves).
6. See United States v. Feliciano, 223 F.3d 102, 109 (2d Cir. 2000).
7. See Mejia, 545 F.3d at 190 citing Dang Vang v. Toyed, 944 F.2d 476, 481-82 (9th Cir. 1991) (upholding the district court’s admission of expert testimony on Hmong culture).
8. See United States v. Nersesian, 824 F.2d 1294, 1308 (2d Cir. 1987),United States v. Castillo, 924 F.2d 1227, 1232 (2d Cir. 1991); United States v. Locascio, 6 F.3d at 939; see also United States v. Tapia-Ortiz, 23 F.3d 738, 740 (2d Cir. 1994) United States v. Dukagjini, 326 F.3d 45 (2d Cir. 2003), and United States v. Lombardozzi, 491 F.3d at 61. In Lombardozzi, the Court affirmed the judgment against the defendant despite its concerns about the government’s expert. In that case, the government expert was an investigator employed directly by the U.S. Attorney’s Office. Not only did the witness testify about the structure of La Cosa Nostra, he testified that the defendant was “a soldier in the Gambino crime family.” The witness on cross examination testified that he based his testimony on “conversations with cooperating witnesses and confidential informants” and his own observations of the defendant’s actions. Unfortunately, his attorney did not raise confrontation clause challenges to this testimony.