Bullet Lead Analysis - Defendants not Told of Flaws in Fbi Technique

Hundreds of innocent people nationwide havepaint and bullet lead. The results of their research
been convicted with the help of an FBI forensicwere published in U.S. Atomic Energy Commission
tool that was discarded over two years ago, andReports (Lukens et al. 1970), the Journal of
the FBI has yet to alert the affected defendantsRadioanalytical Chemistry (Guinn 1982; Guinn et al.
or courts, even as the window for appealing1987), and the Journal of Forensic Sciences
convictions is closing.(Lukens and Guinn 1971).
The Basis for Compositional Bullet Lead AnalysisIn one research effort, the group acquired and
(Comparisons)analyzed samples from bullet lead manufacturers.
BackgroundThe results of these analyses confirmed that a
When the physical markings of a fired bulletcast billet poured from a pot of molten lead is
recovered from a crime scene are too mutilatedrelatively homogeneous, but that leads poured
for visual comparison or the firearm used in thefrom separate molten batches are distinguishable.
crime is not recovered, the bullet can beAs a result, comparative bullet lead analysis has
compared with other bullets associated with abeen adopted by laboratories and accepted by
suspect by its elemental composition.courts internationally (Andrasko et al. 1993;
When a crime-scene bullet contains the sameBlacklock and Sadler 1978; Brandone and Piancone
analytical elemental concentrations (i.e. match in1984; Capannesi and Sedda 1992; Cohen et al.
composition) as the bullets from known1988; Desai and Parthasarathy 1983; Dufosse and
cartridges, a single source of these bullets cannotTouron 1998; Gillespie and Krishnan 1969; Guy and
by excluded. During the manufacturing processes,Pate 1973; Kishi 1987; Krishnan 1973; Krishnan and
thousands of lead specimens (bullets and bulletJervis 1984; Sankar Das et al. 1978; Screenivas et
cores) are produced with analyticallyal. 1978; Suzuki and Yoshiteru 1996).
indistinguishable compositions.The NAA technique used at many laboratories
However, those lead specimens that share thehas been replaced by inductively coupled
same composition are generally packaged withinplasmaoptical emission spectroscopy (ICP-OES),
the same box of cartridges, or in boxes ofpreviously known as inductively coupled
cartridges of the same caliber and type at theplasmaatomic emission spectroscopy (ICP-AES)
same manufacturing plant, on or about the same(Peters and Koons 1988).
date.OES was adopted because people confused AES
When the differences in element concentrationswith auger electron spectrometry (Boss and
are small but analytically significant, a comparativeFredeen 1997). Since the 1970s, ICP-OES has
examination can be used to differentiate amongbeen widely accepted and is the method of
bullets made of different alloys or to exclude achoice for most inorganic analysis (Koons 1993;
single source for bullets of the same alloy.Montaser and Golightly 1987).
Comparative bullet lead analysis was developed inOne advantage of ICP-OES is its ability to
the early 1960s by researchers at Generaldetermine the concentrations of as many as 70
Atomic (now General Activation Analysis, Inc.elements simultaneously in some samples.
located in Encinitas, California) under a federalICP-OES instrumentation is used in environmental,
grant to develop uses for neutron activationmanufacturing, research and forensic laboratories
analysis (NAA).throughout the world and has been used by the
Researchers developed procedures for analyzingFBI Laboratory in casework for the past 12
such materials as gunshot primer residues, glass,years.