Expert Testimony - Expert Evidence Offered by the Government

United States v. Vera, 770 F.3d 1232 (9th Cir. 2014)

This is a lengthy decision that explains what the government may and may not accomplish with expert testimony in gang and drug cases. The government was permitted to introduce expert testimony on issues of gang culture and structure, but improperly admitted expert testimony on drug jargon that purported to translate wiretapped calls. Regarding the coded language expert testimony, there is a difference between an expert who explains and translates commonly used terms and one who explains what terms mean in this case which were encountered for the first time by the expert. If the expert is explaining certain jargon that he has encountered for the first time in this case he must explain the methodology by which he has reached his conclusions. The jury, moreover, must be instructed about the differences between an expert testifying based on his experience with certain terms and his lay opinion testimony based on his familiarity with the people and conversations involved in this case. For example, the agent was asked to explain the statement, “get one and cook it” referred to one ounce of crack cocaine. That is lay opinion testimony, not an expert’s opinion about common drug jargon. The jury should have been instructed that such testimony does not come with the imprimatur of the agent’s expertise.

United States v. Groysman, 766 F.3d 147 (2d Cir. 2014) The Second Circuit reversed this health care fraud conviction on the basis of several “egregious” evidentiary errors committed at trial. The defendant was charged with conspiring with a company that supplied durable medical equipment to prepare false invoices. The wholesaler was cooperating and taped many of the conversations, though many were inaudible. The government offered testimony from its case agent for several days at the start of trial. The agent (1) offered inadmissible bolstering testimony by testifying that certain transactions occurred, based only on his interviews of the cooperators – he had no personal knowledge to verify that these transactions occurred; (2) offered a summary chart which was not a summary of voluminous evidence, but simply a recitation of what he was supposedly told by the cooperators, thus violating both the hearsay rules and the bolstering rules and the rule governing the admissibility of summary charts; (3) the use of the agent to summarize the case at the outset was improper because it amounted to opinion testimony. The Second Circuit, as noted above, characterized these evidentiary errors as egregious and supported a plain error standard of review reversal.

United States v. Medina-Copete, 757 F.3d 1092 (10th Cir. 2014)

The defendant, an alleged drug courier, was extremely nervous when she was stopped by the state police. She started reciting a prayer. The government introduced expert testimony from a law enforcement officer who also professed to have expertise in various Mexican shrines of drug trafficerks. He testified that the prayer recited by the defendant was an indication that she was a drug courier based on the content of the prayer. The Tenth Circuit reversed the conviction based on this improper testimony linking a religious icon to drug traffickers.

United States v. Garcia, 752 F.3d 382 (4th Cir. 2014)

Allowing an FBI agent to testify as a fact witness and also as an expert on slang interpretation was reversible error in this case. The problem is that having cloaked the witness with “expert” status, the witness’s fact testimony is given special credence. In addition, the “expertise” in this case was derived from talking to other people in this investigation, which creates hearsay and Confrontation Clause problems. The agent testified that she “confirmed” her understanding of certain codes by talking to arrested co-conspirators. Additionally, the expert would simply recite what actually occurred during the course of the investigation (for example, the seizure of a certain quantity of drugs) and then explain that this seizure was the basis for her expert opinion that a previous conversation related to the transaction that was the subject of the seizure. This is not expert testimony, but simply argument. Finally, the expert provided no basis for many of her expert “de-coding” opinions. She did not explain that the same code was used in another conspiracy she investigated, or from her experience in other cases, or from some other training. For example, she stated that “590” meant “590 grams of heroin” or “2” meant $200.00.

United States v. Hill, 749 F.3d 1250 (10th Cir. 2014)

After the defendant’s statement was played in court, the government called an “expert” FBI agent who had training in determining if a person was being truthful or not and he offered his expert opinion that the defendant was not being truthful. Among other reasons, the agent found the defendant lacked credibility because he said, “I swear to God” and other statements that showed that he invoked his belief system, rather than relying on facts to support his protestations of innocence. The Tenth Circuit held that this was reversible error even in the absence of an objection by the defense attorney. Juries are tasked with making credibility decisions, not government experts.

United States v. Ramirez-Fuentes, 12-1494 (7th Cir. 2013)

The government elicited testimony that the methamphetamine involved in this case was “Mexican methamphetamine.” The Seventh Circuit held that this was reversible error.

United States v. Haynes, 729 F.3d 178 (2d Cir. 2013)

A police officer was permitted to offer testimony about how a gas tank works (i.e., how the fuel gauge reflects the amount of fuel in the tank), which was relevant to whether the defendant was aware that drugs were hidden in the fuel tank. The testimony should not have been admitted as opinion testimony. The testimony should only have been offered as expert testimony after the discovery rules and the witness’s expertise was proven. Another witness – the government’s expert witness – was improperly permitted to offer expert testimony that the defendant was aware that there were drugs in the gas tank. This testimony was inadmissible pursuant to Rule 704(b), which prohibits expert testimony on a defendant’s mental state at the time of a crime.

United States v. Hampton, 718 F.3d 978 (D.C. Cir. 2013)

The testimony of an FBI agent, interpreting and explaining recorded phone conversations of the defendants was inadmissible and admitting this testimony was reversible error. The government offered the testimony as lay opinion testimony, with the agent explaining that he formed his opinion about the meaning of the conversations based on having listened to countless hours of the conspirators’ conversations.

United States v. Santini, 656 F.3d 1075 (9th Cir. 2011)

The defendant was caught at the border bringing marijuana into the country. He claimed that because of a brain injury, he was subject to being tricked and presented a psychiatrist to support the defense. The prosecutor also presented an expert witness who testified that based on his review of the defendant’s “rap sheet” this defense was invalid, because he had run-ins with the law prior to the injury. The Ninth Circuit reversed the conviction: the rap sheet was unreliable and did not distinguish arrests from convictions and was otherwise not probative of the defendant’s state of mind in connection with the present case. The government’s argument tha the evidence was admissible to explain the expert’s opinion was also unavailing, because pursuant to Rule 702, the expert must base his opinions on reliable information.

United States v. Morin, 627 F.3d 985 (5th Cir. 2010)

The government’s expert offered improper expert testimony about drug courier profile evidence in certain respects. The expert “interpreted” a surveillance video and testified that her interpretation of the events was typical of how drug conspirators operate.

United States v. Gonzalez-Rodriguez, 621 F.3d 354 (5th Cir. 2010)

A DEA agent should not have been allowed to tetify as an expert about the methods drugs are brought into the United States from Mexico. To some extent, the testimony violated Rule 704(b)’s prohibition on testimony about the mental state of the defendant. The court noted that testimony about a drug courier’s profile was improper, because profile evidence is inadmissible. (e.g., “drug couriers generally have no criminal record”). The implication – “the defendant must be a culpable drug courier because he has no criminal record” – was illogical. Harmless error.

United States v. Johnson, 617 F.3d 286 (4th Cir. 2010)

The government offered the testimony of a DEA agent to “interpret” and explain the meaning of wiretapped phone calls. The agent was never tendered as an expert. The testimony was not properly admitted as opinion testimony under Rule 701, because the agent did not observe the events about which he was testifying. Even if he had been tendered as an expert, the government did not offer any evidence explaining the agent’s “methodology or guiding principles that would enable him to decode the wiretapped phone calls in this case.”

United States v. Cooks, 589 F.3d 173 (5th Cir. 2009)

The government used an FDIC investigator as an expert in the area of mortgage fraud. Though the agent had some training in fraud investigation, he had no specialized training in the area of mortgage fraud and had never previously testified as an expert in this field. Qualifying the agent as an expert was erroneous, but harmless error.

United States v. Martinez, 588 F.3d 301 (6th Cir. 2009)

During the direct or cross-examination of an expert witness, the witness may refer to statements in a learned treatise. Portions of the treatise may be read into evidence, though the treatise itself is not admissible. The portion of the treatise is admissible for the truth of the matter asserted and Rule 803(18) exempts the statements from the hearsay rule. In this case, during the testimony of the expert, the government introduced a videotape of an expert describing a medical procedure. The Sixth Circuit held that a videotaped interview of the expert did not qualify under Rule 803(18).

United States v. Mejia, 545 F.3d 179 (2d Cir. 2008)

The government offered the testimony of an expert in this gang case. The expert offered testimony about the structure of the gang, its history and various other matters that was not admissible because (1) the testimony was not based on any data or information that was the proper subject of expert testimony; (2) the testimony included the expert’s lay opinion, rather than expert opinion; (3) the expert simply repeated some things he was told by co-conspirators and was therefore testimonial hearsay in violation of Crawford. Reversible error.

Ege v. Yukins, 485 F.3d 364 (6th Cir. 2007)

Bite mark evidence offered by the state in this trial had no foundation and should not have been admitted. The expert for the state testified that nobody else in the Detroit Metropolitan area had similar “dentition.” Without any foundation for this expert testimony the evidence was inadmissible and was a violation of the defendant’s right to due process. Chambers v. Mississippi, 410 U.S. 284 (1973).

United States v. White, 492 F.3d 380 (6th Cir. 2007)

Testimony offered by employees of Medicare fiscal intermediaries about the mechanics of Medicare reimbursement, as well as defining “related-party transactions” and “reasonable costs” qualified as “expert testimony.” The government did not qualify these witnesses as experts and failed to provide the required Rule 16 discovery regarding their testimony. Harmless error.

United States v. Ibarra, 493 F.3d 526 (5th Cir. 2007)

The government asked its agent about the notion that a driver of a truck would not know that his truck contained a large quantity of cocaine. The agent testified that in his experience, he had never seen a courier entrusted with an amount of cocaine that size ($4 million) without the courier knowing that he was carrying something illegal. The Fifth Circuit held that this was improper expert testimony (not beyond the knowledge of a typical juror, and thus not in need of expert analysis) and was reversible error in this case.

United States v. Ganier, 468 F.3d 920 (6th Cir. 2006)

A government computer expert who utilized a forensic program to mine information from the defendant’s computer qualified as an expert whose testimony was subject to Rule 16(a)(1)(G). Though the expert relied on a forensic tool that was available to the public, the testimony was nevertheless of an expert nature and was therefore covered by the Rule.

United States v. Lopez-Medina, 461 F.3d 724 (6th Cir. 2006)

It was reversible error for the trial court to fail to instruct the jury about the dual role of the government’s case agents as both expert witnesses and fact witnesses. As experts, the agents testified that the defendant’s conduct was consistent with the actions of someone conducting counter-surveillance and that certain scraps of paper were drug ledgers and that other evidence was “drug wrapping” material.

United States v. Garcia, 413 F.3d 201 (2d Cir. 2005)

A DEA agent may not testify, either as an expert, or as a matter of his lay opinion, about the defendant’s role in the conspiracy based on the totality of his experience. When an agent testifies as a matter of lay opinion, the opinion must be base on his personal observations, not his evaluation of all the evidence, or the totality of the investigation. This opinion explains in some detail the requirements for lay opinion testimony, and concludes that the government satisfied none of the requirements for offering lay opinion testimony.

Howard v. Walker, 406 F.3d 114 (2d Cir. 2005)

A co-conspirator’s statement to the police was excluded on Bruton grounds. However, an expert witness for the state relied on that statement in reaching her conclusion that the victim’s death was caused by conduct of the conspirators. Though an expert may generally rely on inadmissible evidence in reaching a conclusion, including hearsay, that rule assumes that an expert will carefully analyze the basis of his opinion and that the trial court will conduct a sufficient Daubert hearing to ensure the reliability of the expert’s underlying data from which she draws her conclusion. In this case, the unreliable statements of the co-conspirator were not reliable and the expert’s opinion was therefore improperly admitted. The error was compounded by the state trial court’s ruling that if the defense cross-examined the witness about her conclusions, the inadmissible Bruton statement would be admitted. A defendant cannot be compelled to sacrifice one right – the Sixth Amendment right to cross-examine witnesses – to protect another right – i.e., the right of Confrontation embodied in the Bruton doctrine. Simmons v. United States, 390 U.S. 377 (1968).

United States v. Miller, 395 F.3d 452 (D.C. Cir. 2005)

Though finding no error, the D.C. Circuit in this case cautioned that when questioning an expert on the practices of drug organizations, the questions should not be phrased in such a way as to amount to a carbon copy of the evidence at trial. Additionally, the expert should carefully explain that he is testifying about his knowledge of drug organizations in general, not the particular drug organization on trial, in order to eliminate the possibility that the jury will conclude that the “expert” has reached a decision about the case on trial.

United States v. Abreu, 406 F.3d 1304 (11th Cir. 2005)

The Eleventh Circuit concludes that fingerprint evidence meets the Daubert standard.

United States v. Grinage, 390 F.3d 746 (2d Cir. 2004)

The Second Circuit reverses this conviction on the basis that an agent was permitted to testify about the meaning of wiretapped phone calls. The government argued that the agent was not qualified as an expert and did not purport to translate coded calls, but was simply offering opinion testimony based on a review of all the calls. The Second Circuit rejects these arguments. An agent may not offer his opinion of “all the calls” and ask the jury to accept that interpretation. Moreover, the agent was basing his testimony on more than simply his having listened to the calls; he testified that he based his opinion also on his knowledge of “the entire investigation.” Reversible error.

United States v. Frazier, 387 F.3d 1244 (11th Cir. 2004)

In this en banc decision, the Eleventh Circuit thoroughly reviews the law regarding the admissibility of expert testimony and the application of Daubert to testimony offered by an expert on a matter of his expertise. In this case – which is ultimately resolved in favor of the government – the trial court excluded testimony from the defendant’s expert (a forensic investigator) about what “would have been expected” had the defendant and the victim had sexual intercourse in a car. The victim claimed to have been raped in the car; the defendant claimed that they did not have sex. There was no physical evidence found in the car (such as pubic hair, or seminal fluid). The en banc decision decided that this was not an abuse of discretion. On the other hand, the government was permitted at trial to introduce testimony from its expert that scientific research established that there was frequently no “transference” of pubic hair in cases of sexual assault. Though the decision focuses on the specific testimony being offered by the different experts (the defendant’s expert based his conclusion on vague “what he expected” standard, while the government’s expert had scientific studies that revealed actual statistics), the decision thoroughly reviews the type of Daubert analysis required by the trial court before offering what might be described as “junk” expert testimony.

Earls v. McCaughtry, 379 F.3d 489 (7th Cir. 2004)

The defendant was charged with molesting a six-year old child. There were no witnesses to the events and no physical evidence corroborating the child’s statements. A social worker who interviewed the child and testified as an expert said that she believed the child. This was inadmissible evidence and the attorney’s failure to object amounted to ineffective assistance of counsel. In addition, during the videotape of the child prepared by the social worker, the social worker told the child that she believed her and the defendant should not have done that to her. The attorney’s failure to redact the tape was ineffective assistance of counsel.

United States v. Dukagjini, 326 F.3d 45 (2d Cir. 2003)

The government should not be permitted to use a fact witness, such as a case agent, to also offer expert testimony. In this case, the case agent, who testified as a fact witness, also offered expert testimony about drug jargon. A considerable amount of his “expert” testimony was based on his consideration of the evidence in this case, as opposed to his former experience and knowledge. One problem with this procedure is that juries will add undue weight to the witness’s fact testimony. Harmless error.

United States v. Mitchell, 365 F.3d 215 (3rd Cir. 2004)

In a forty page opinion, the Third Circuit evaluates the admissibility of fingerprint evidence under the Daubert and Kumho Tire standards and ultimately concludes that such evidence passes Daubert muster and was properly admitted in this case.

United States v. Casas, 356 F.3d 104 (1st Cir. 2004)

The government’s case agent, the first witness to testify, was permitted, over objection, to “name the members of the organization” that was involved in drug dealing (which, of course, included numerous of the defendants on trial). Some of the agent’s testimony was based on what other conspirators told him during their debriefings. This testimony was not admissible as summary evidence, because the underlying facts were not in evidence. In fact, he was offered as an “overview witness” not a summary witness. See also United States v. Griffin, 324 F.3d 330 (5th Cir. 2003). The testimony violated the confrontation clause. The testimony was not proper expert testimony because there was nothing about his testimony that was the proper scope of expert testimony. With regard to certain defendants, the error was reversible error. See also United States v. Flores-De-Jesus, 569 F.3d 8 (1st Cir. 2009).

United States v. Cruz, 363 F.3d 187 (2d Cir. 2004)

The defendant was asked by a drug dealer to “watch his back” while he finished a deal. A DEA agent testified as an expert (and also as a fact witness) that “watch his back” was drug code for act as surveillance during a drug deal. The Second Circuit held that trial court erred in admitting this expert testimony. The agent was not able to explain why the slang term referred to a drug deal, as opposed to some other criminal (or for that matter, innocent) conduct. The court stressed the dangers inherent in allowing an agent to testify as both an expert and a fact witness. See also United States v. Dukagjini, 326 F.3d 45 (2d Cir. 2003). The court reversed the conviction, holding that the evidence was insufficient, even considering the agent’s expert testimony.

United States v. Mendoza-Medina, 346 F.3d 121 (5th Cir. 2003)

Though it was harmless error, the trial court should not have permitted the government to use a DEA agent to testify as an expert witness about matters regarding the methods by which drug couriers do their work. Testimony such as “they bring their families along to disguise their mission” and “drug dealers don’t trust unwitting couriers” and similar words of wisdom were not the proper subject of expert testimony. See also United States v. Gutierrez-Farias, 294 F.3d 657 (5th Cir. 2002); United States v. Ramirez-Velasquez, 322 F.3d 868 (5th Cir. 2003).

United States v. Williams, 343 F.3d 423 (5th Cir. 2003)

In this civil rights prosecution (a law enforcement officer shooting a suspect), the government called other officers to testify that the shooting was not reasonable. This was error, because the question of reasonableness was a legal question and an expert may not offer an opinion about the law. Harmless error.

United States v. Pablo Varela-Rivera, 279 F.3d 1174 (9th Cir. 2002)

The trial court committed reversible error in allowing the government to introduce DEA expert testimony regarding the structure of drug trafficking operations, as well as their modus operandi and the fees paid to couriers. Such evidence is not admissible in a case, such as this case, where the defendant is not charged with being a member of a conspiracy. See also United States v. Vallejo, 237 F.3d 1008, 246 F.3d 1150 (9th Cir. 2001); United States v. McGowan, 274 F.3d 1251 (9th Cir. 2001).

United States v. Hermanek, 289 F.3d 1076 (9th Cir. 2002)

If an expert testifies about the use of code words, even though he has not heard the words used that way before, the government must satisfy the requirements of Daubert. It appeared that in this case, the agent concluded that the various references to “watches” and “cookies” in the taped conversations were actually references to drugs, based simply on the agent’s belief that the participants in the calls were drug dealers. Such circular logic does not satisfy Rule 702. Harmless error.

Snowden v. Singletary, 135 F.3d 732 (11th Cir. 1998)

Permitting an expert witness to testify that 99.5% of children tell the truth in child abuse cases was a denial of fundamental fairness and in the circumstances of this case, where the child's credibility was the central issue, required setting aside the conviction.

United States v. Cruz, 981 F.2d 659 (2d Cir. 1992)

Expert testimony in this case was improper for two reasons: (1) the expert testified that the area of the drug transaction was heavily Hispanic and “drug-inundated.” Because all the defendants were Hispanic, this was improper and prejudicial; (2) the defendant claimed he was not on the scene; the expert testified that the conduct of the defendant as described by witnesses was characteristic of a drug broker. This amounted to improper bolstering of the witness’s testimony and was not the proper subject of expert testimony. Any juror who watches TV, movies, or the news, knows that drug dealers attempt to hide their identity.

United States v. Boissoneault, 926 F.2d 230 (2d Cir. 1991)

The trial court should not have allowed an agent to conclude that all the physical evidence in the case suggested that the defendant was involved in the street level distribution of cocaine. Such a conclusion was not beyond the ken of the jury. Furthermore, even assuming the admissibility of this testimony, the evidence was insufficient to support a conviction of possession with intent to distribute. The defendant was arrested after a traffic stop. He had none of the typical paraphernalia of a distributor. He had a ledger (which the agent described as a drug accounts receivable ledger), $1,460 in cash and 5 grams of cocaine. Only a possession offense could be upheld.

United States v. Castillo, 924 F.2d 1227 (2d Cir. 1991)

A narcotics officer’s expert testimony about the practices of drug dealers led to a reversal of this conviction. The officer testified that drug dealers often force customers to ingest cocaine, at gunpoint, in order to ensure that the customer is not an undercover agent. Such matters are not beyond the ken of the jury and are thus not the appropriate subject of expert testimony under Rule 702.

United States v. Scop, 856 F.2d 5 (2d Cir. 1988)

A defendant’s perjury prosecution was based on answers he gave to questions which contained the term “manipulation.” At trial, the government was permitted to offer expert testimony on the definition of the word “manipulation.” It was error to admit this testimony and the perjury conviction could not stand. The Court dealt with other issues relating to the improper expert testimony at 846 F.2d 135.

United States v. Scop, 846 F.2d 135 (2d Cir. 1988)

The Second Circuit reversed a conviction because a witness gave expert testimony couched in terms of legal conclusions. The expert testified, in language of the criminal code, that the defendants were “direct” and “material” participants in a “fraudulent” and “manipulative” scheme to artificially inflate stock prices. The court holds that this is improper expert testimony. An expert may, for example, give an opinion that a defendant participated in a drug transaction, but an expert may not testify that the defendant possessed heroin with intent to sell. The trial court also erred in admitting a prosecution expert witness to give his opinion as to the credibility of other prosecution witnesses.

United States v. Armendariz-Mata, 949 F.2d 151 (5th Cir. 1991)

The DEA agent’s “expert” testimony that the defendant was a “knowledgeable drug trafficker” was not proper under Rule 702: this testimony was totally unnecessary to the jury and did not help them understand the issues.

Cooper v. Sowders, 837 F.2d 284 (6th Cir. 1988)

The Sixth Circuit condemns a police officer’s testimony that, in his opinion, the other suspects in the case were not linked to the crime. There was nothing scientific, technical, or specialized about the officer’s testimony.

United States v. Quigley, 890 F.2d 1019 (8th Cir. 1989)

The trial court erred in permitting the government to introduce expert testimony about the characteristics of a typical drug courier. The government used such evidence to argue that the defendant, who possessed a kilogram of cocaine in his car, intended to distribute it. The evidence in this case was not used to explain or justify an investigative stop, but as substantive evidence that because he fit the profile he therefore intended to distribute what was in his possession.

United States v. Roy, 843 F.2d 305 (8th Cir. 1988)

It was error, although harmless, to permit a law enforcement officer to give his opinion as to the truthfulness of the defendant’s accomplices’ testimony. Human lie detectors are not permissible in court.

United States v. Figueroa-Lopez, 125 F.3d 1241 (9th Cir. 1997)

Testimony of law enforcement officers that the defendant’s actions were consistent with those of experienced drug traffickers was improperly admitted in this drug prosecution as lay opinion testimony. The witness was not qualified as an expert.

United States v. Blackstone, 56 F.3d 1143 (9th Cir. 1995)

The defendant was charged with being a felon in possession of a firearm. The gun was found in his truck. Also found in the truck was a methamphetamine recipe. The government was permitted to offer expert testimony from a DEA agent to the effect that guns and meth labs go together. This was error. Not only should the expert testimony not have been admitted, the recipe itself was not admissible because its probative value was outweighed by its prejudicial impact.

United States v. Gillespie, 852 F.2d 475 (9th Cir. 1988)

The government failed to qualify its expert testimony under the Frye test in this trial involving allegations of child sex abuse. The expert testified that the child’s behavior with anatomically correct dolls demonstrated that she had been abused by a man and not a woman. The trial court erred in holding that testimony relating to a child’s behavior with anatomically correct dolls does not constitute expert opinion. Also, the court held that it is error to permit an expert to testify that the defendant exhibited characteristics typical of child molesters.

United States v. Messner, 107 F.3d 1448 (10th Cir. 1997)

In this bankruptcy fraud trial, the trial court erred in permitting the government to introduce expert legal testimony about a bankrupt’s duty to disclose assets. Harmless error.

United States v. Zimmerman, 943 F.2d 1204 (10th Cir. 1991)

The defendant, an attorney, was charged with conspiracy to commit bankruptcy fraud. The government offered the statements of two bankruptcy judges, made in the course of the bankruptcy proceedings, to the effect that the attorney was either negligent, or was part of a conspiracy. This was inadmissible and necessitated reversal of the conviction.

United States v. Boyd, 55 F.3d 667 (D.C.Cir. 1995)

Pursuant to Rule 704(b), an expert witness may not testify whether a defendant has the requisite state of mind to satisfy an element of the offense. In this case, the defendant, who was conversing with another individual, was seen holding a bag which contained 5 grams of crack cocaine. When the police approached him, he ran and threw the bag under a truck. A law enforcement officer was posed these facts in the form of a hypothetical and he opined that the defendant possessed the cocaine “with intent to distribute it.” This violated Rule 704(b).

United States v. Mitchell, 996 F.2d 419 (D.C.Cir. 1993)

An officer was asked what the defendant intended in light of his arrest in possession of nine individually wrapped bags of cocaine. The officer responded that in his opinion, the defendant intended to distribute the cocaine. This violated Rule 704(b) which outlaws the use of expert testimony about the defendant’s mental state relating to an element of the offense. Because defense counsel did not object on these grounds, however, this was not reversible error.

United States v. Doe, 903 F.2d 16 (D.C.Cir. 1990)

The conviction of two Jamaican drug dealers was reversed because of the improper testimony of police detectives that persons of Jamaican descent were “taking over the distribution of drugs in D.C.” This testimony was unfairly prejudicial and outweighed any probative value under Rule 403. Furthermore, the prosecutor repeatedly referred to the defendants as “the Jamaicans” which created a potential for prejudice on the part of the jurors.