Drug Contamination of U.S. Paper Currency and Forensic Relevance of Canine Alert to Paper Currency: A Critical Review of the Scientific Literature

Abstract

Several studies have reported on wide-spread contamination of U.S. paper currency with cocaine and to a lesser extent other illicit drugs. Canines are trained and employed to search for and alert to drugs. Canine alert to currency has been used as evidence that currency has been directly involved in illicit drug trafficking to justify currency seizure and forfeiture. This assertion, particularly when the only evidence is based upon canine alert, has been challenged in the courts considering that most currency in circulation is contaminated with cocaine. Comprehensive review of the scientific literature establishes that (i) 67-100% of circulated U.S. currency is contaminated with cocaine ranging from a few nanograms to over one milligram/bill (ii) various biological and environmental parameters impact canine alert to drugs. It is concluded that canine alert to U.S. currency is not sufficiently reliable to determine that currency was directly used in an illicit drug transaction.

Determination of cocaine on banknotes using innovative sample preparation coupled with multiple calibration techniques

“…The widespread contamination of paper currency is believed to be due to the innumerous extent of cocaine distribution, transaction, and consumption 2–4 . Reports have shown that banknotes were contaminated with cocaine residue 2–7 . Cocaine is often snorted up the nose through rolled‐up bills.…”

“…Sorting machines in financial institutions may also cause cross‐contamination, with an average detected value of 2.67 ng per note 2,8 . The presence of cocaine on paper currency provides an interesting and comprehensive framework of drug testing, research in forensic science, and of educational instruction in analytical chemistry 2–5,9,10 . The chemical structure of cocaine is shown in Figure 1.…”

“…[2][3][4] Reports have shown that banknotes were contaminated with cocaine residue. [2][3][4][5][6][7] Cocaine is often snorted up the nose through rolled-up bills. Sorting machines in financial institutions may also cause cross-contamination, with an average detected value of 2.67 ng per note.…”

“…2,8 The presence of cocaine on paper currency provides an interesting and comprehensive framework of drug testing, research in forensic science, and of educational instruction in analytical chemistry. [2][3][4][5]9,10 The chemical structure of cocaine is shown in Figure 1.…”

Isobutylene contamination of blood collected in 10‐ml evacuated blood collection tubes with gray conventional rubber stoppers

“…The potential for evidence contamination in forensic laboratories has received increased scrutiny since the introduction of DNA analysis [1,2]. The contamination of paper and plastic currency with low concentrations of drugs has been reported [3][4][5][6]. This potential contamination complicates the interpretation of laboratory results used in the identification of drug money in forfeiture cases and identification of money used as drug paraphernalia.…”