Drug Detection Dog Allegedly Sniffs Out “Innocent Environmental Contamination” In Trafficking Case


Chemistry Expert

Court: United States District Court for the Eastern District of North Carolina, Eastern Division
Jurisdiction: Federal
Case Name: United States v. $307,970.00 in United States Currency
Citation: 2019 U.S. Dist. LEXIS 84342


In this drug trafficking case, the plaintiff filed a complaint for forfeiture in rem against $307,970.00 in U.S. currency. It was alleged that the currency in question was intended to be used in exchange for controlled substances in violation of Title II of the Controlled Substances Act, 21 U.S.C. §§ 801 et seq.

On the day of the incident, the claimant met with an undercover drug interdiction officer to arrange transport of the currency to Mexico. While transporting the currency in a car, the claimant was stopped by an FBI Task Force Officer for allegedly committing a traffic violation. The FBI Officer was given consent to search the vehicle and discovered the currency concealed within vacuum-sealed plastic bags. The parties disputed whether the claimants collectively had enough legitimate income to account for the currency.

The FBI Officer then summoned a drug detection dog and dog handler to conduct a sniff for drugs. The police dog detected drugs in the currency found in the car. The claimants alleged that the lay witness testimony of the dog handler regarding the dog’s discovery was unreliable, and moved to exclude it. The claimant further denied the alleged connection between the seized currency and drug trafficking, and sought for the currency to be returned.

The Expert

The plaintiff retained an expert witness in chemistry and forensic science to opine on the validity of the claimant’s allegation that the dog sniffed out “innocent contamination” in the currency.

The chemistry expert held a Ph.D. in analytical chemistry and served as a professor at Florida International University’s Department of Chemistry and Biochemistry for more than 30 years. In addition, the expert had published more than 30 papers, and conducted experiments on, the ability of canines to use olfactory senses to detect the presence of drugs in a sample. The chemistry expert had also helped coordinate Florida’s detector dog training and certification program and served in various organizations that worked towards improving the detection capabilities of dogs.

In order to formulate his opinion and testimony, the chemistry expert relied on scholarly literature about currency contamination as well as his own experiments. Based on this research, the expert testified that the levels of cocaine tested were far greater than the average amount of cocaine reported for U.S. currency in circulation.

The dog’s handler had testified that the detection dog’s behavior was consistent with how police dogs act when coming in contact with traces of controlled substances, and the chemistry expert supported this claim. The expert concluded that the detection dog’s senses were triggered by the presence of methyl benzoate, a by product of cocaine. The chemistry expert further opined that if a drug detection dog smells drugs on currency, the amount of drugs is not residual, rather, the dog’s detection indicates that the quantity of drugs is the result of recent illegal activity.  He also claimed the dog’s detection could not be the result of any “innocent environmental contamination” of circulated United States currency by microscopic traces of cocaine.

The claimant sought to exclude this testimony, claiming that the results of the chemistry expert’s studies were incorrect.


The court noted that the chemistry expert was trained enough to provide reliable testimony about a canine’s underlying ability to detect the presence of drugs through smell. The court pointed to the expert’s credentials as more than sufficient to qualify him to discuss the issues at hand in the case.

The court also noted that the chemistry expert’s opinion that innocent contamination does not explain the detection of drugs was reliable because he had performed dozens of experiments, both in controlled environment and on the field, to determine that (1) there is no detectable innocent contamination of methyl benzoate in currency among circulation, and (2) canine senses are triggered by the presence of methyl benzoate at concentration levels much higher than in pharmaceutical cocaine. The expert also used peer-reviewed studies and multiple experiments to support his theory.

The court also noted that the claimant’s objections to expert’s methodology would be better dealt with during cross-examination, as they affected the weight of his opinion, not its admissibility. The court also noted that the chemistry expert’s opinion was reliable as he had based his report on “a positive alert to United States currency by a properly trained narcotics detection canine.” Moreover, the court noted that the chemistry expert was allowed to base his opinion on the testimony of the dog handler because he had also relied on investigation reports, dash camera footage of the search, canine certifications, and training reports.


The chemistry expert witness’ testimony was deemed admissible under the Federal Rules of Evidence, Rule 403.