Analysis of Bank Dye Evidence and the Challenges of Daubert Hearings

Article excerpt


The admissibility of scientific evidence has been affected by a Supreme Court decision made in Daubert v. Merrell Dow Pharmaceuticals (509 U.S. 579 [1993]), which led federal trial judges to become "gatekeepers" of scientific evidence. Judges are responsible for evaluating scientific testimony to determine if it is both relevant and reliable material for the case at hand. Prior to this decision, the admissibility of scientific evidence was governed predominantly by the ruling in Frye v. United States (54 App. D.C. 46, 293 F. 1013, 1014 [1923]). In Frye, the Court found that the admissibility of scientific testimony involving novel techniques must be "generally accepted within the particular field in which it belongs." The responsibility for allowing scientific testimony relied on the opinions of scientists within the relevant field. This posed a problem for juries that did not possess the necessary knowledge for determining if the material being presented was valid or not. The Daubert decision provided the guidelines that were needed to make such an evaluation.

Subsequent to the Daubert ruling, the subject of allowing scientific testimony was readdressed and reaffirmed in two other cases, General Electric Co. v. Joiner (522 U.S. 136 [1997]) and Kumho Tire Co. v. Carmichael (526 U.S. 137 [1999]). In Joiner, the Court upheld the trial court's gatekeeping function regarding admitting scientific evidence when an abuse of discretion is absent. In Kumho, the Court held that the gatekeeper function of the judge shall apply to all expert testimony, including that which is nonscientific. Although the FBI Laboratory has never encountered a Daubert challenge for the analysis of bank dye-pack evidence, this article addresses how the analysis of bank dye-pack evidence can meet the challenges of a Daubert hearing.


A bank security dye pack resembles a real stack of bills that contains an electronic device disguised within a hollowed portion of the stack (Figure 1). The pack remotely activates to discharge soon after a robber exits the bank with the device. When activated, the device emits a steady aerosol stream that contains a red dye and may also emit tear gas (Figure 2). The purpose of the device is for the dye to stain the suspect, money, and other items in close proximity, and the tear gas is used to encourage abandonment of the money, thus making it easier to recover.



Analysis of evidence related to bank robbery incidents involves the identification of chemical residues associated with a dye pack, in particular, the red dye (1-methylaminoanthraquinone [MAAQ]) and CS tear gas (orthochlorobenzalmalononitrile). The standard operating procedure performed at the FBI Laboratory involves a multistep plan that incorporates several different techniques to identify MAAQ and CS tear gas. The chemical residues first must be visualized by examining the item for red and/or pink stains or, in the case of dark items, swabbing an item with a clean swab moistened with a solvent such as methanol or acetone. Once the colored stain is isolated, it is extracted with an appropriate chemical solvent. The liquid solvent then can be analyzed by thin-layer chromatography and gas chromatography-mass spectrometry (GC-MS) in electron impact (EI) and/or chemical ionization (CI) mode.

The presence of both chemicals, MAAQ and CS tear gas, is unique to bank security devices. However, each chemical by itself can be found in other products. MAAQ previously had been used in some colored smoke grenades for the military, but those formulations have since changed. The plastics industry sometimes uses MAAQ, and it may be found in products such as automotive taillight lenses, styrene bins, and billboards. Because the dye is very stable in such matrices, it is very difficult to remove from such materials and would require a chemical extraction. …