Forensic significance of bullet lead compositions

The concentrations of seven elements in projectile lead specimens received as evidence were used to assess the frequency of the occurrence of two unrelated samples having indistinguishable compositions. A set of data from 1837 samples was selected for this study from a sampling of 23,054 lead bullets and shot pellets received as evidence in the FBI Laboratory over the period 1989 through 2002. The method used for selection of samples from case submissions ensured that no two samples of the same general type from the same case were included and that no bias was introduced concerning representation of manufacturers or production sources. A total of 1,686,366 pairwise lead sample comparisons were made using the concentrations of the elements Sb, Cu, As, Ag, Bi, Sn, and Cd using a match criterion of two times the sum of the standard deviations of the paired samples. Of the 1837 samples, 1397 samples, or 76%, are distinguishable from every other sample in this study. The total number of indistinguishable sample pairs is 674, for a frequency of 1 out of every 2502 comparisons. The frequency of occurrence of matching samples decreases as the number of measured elements is increased and as the precision of the measurements improves. For bullets in which all seven elements were determined, the match frequency is 1 in 7284. Compositional comparison of bullet lead provides a reliable, highly significant point of evidentiary comparison of potential sources of crime-related bullets.     

A metallurgical review of the interpretation of bullet lead compositional analysis

Comparison of the minor and trace element compositions of bullet lead alloys has been used by some forensic examiners to make definitive positive associations between bullets or lead fragments at a crime scene and samples of bullets linked to a suspect(s). Such conclusions have been based on the elemental analysis of isolated groups of bullets with no consideration of the metallurgical processes involved in the production and refining of the bullet lead alloys. An understanding of the metallurgy of lead refining reveals that the elements quantified in the forensic analysis are carefully controlled in the refining process and that there are logical reasons why some elements are more discriminatory than others. Data for lead alloys supplied to two major ammunition manufacturers confirm that multiple indistinguishable shipments of lead alloys from secondary lead refiners to the ammunition manufacturers are made each year and over a period of many years. The data also demonstrate that distinguishable compositions can come from the same melt or "source" of lead alloy. These results clearly indicate that bullets with indistinguishable compositions could have come from different lead "sources" produced in the same or different years. Furthermore, the observation that two bullets have a distinguishable composition does not necessarily mean that they came from a different "source".Our results show that the forensic examiner using a method of bullet lead alloy elemental analysis, which quantifies up to six elements is restricted to concluding only that indistinguishable bullets might have come from the same "source," not that they did come from the same "source". In addition, it is quite possible that multiple bullets with similar but distinguishable compositions could have come from the same "source". The authors therefore feel that there is no scientific validity to any conclusions more positive than attributing the possible association as to molten source among bullets from different samples. An understanding of the metallurgical principles operative in the melting/casting process as well as the data acquired for this study, indicate that any forensic conclusions which associate unknown bullets with the "same source", and/or "same box" should fail most or all Daubert criteria.     

Proper assessment of the JFK assassination bullet lead evidence from metallurgical and statistical perspectives

The bullet evidence in the JFK assassination investigation was reexamined from metallurgical and statistical standpoints. The questioned specimens are comprised of soft lead, possibly from full-metal-jacketed Mannlicher-Carcano (MC), 6.5-mm ammunition. During lead refining, contaminant elements are removed to specified levels for a desired alloy or composition. Microsegregation of trace and minor elements during lead casting and processing can account for the experimental variabilities measured in various evidentiary and comparison samples by laboratory analysts. Thus, elevated concentrations of antimony and copper at crystallographic grain boundaries, the widely varying sizes of grains in MC bullet lead, and the 5-60 mg bullet samples analyzed for assassination intelligence effectively resulted in operational sampling error for the analyses. This deficiency was not considered in the original data interpretation and resulted in an invalid conclusion in favor of the single-bullet theory of the assassination. Alternate statistical calculations, based on the historic analytical data, incorporating weighted averaging and propagation of experimental uncertainties also considerably weaken support for the single-bullet theory. In effect, this assessment of the material composition of the lead specimens from the assassination concludes that the extant evidence is consistent with any number between two and five rounds fired in Dealey Plaza during the shooting.     

利用SEM/EDS区别小口径手枪及六四式手枪在纺织品上的枪击孔

利用扫描电子显微镜和能谱仪（SEM/EDS）对小口径手枪、六四式手枪在纺织品上枪击孔洞处的附着物进行了观察分析,较好地解决了判定是小口径手枪还是六四式手枪射击问题。     

The application of lead isotope analysis to bullet individualization in two homicides.

Bullets were characterized by lead isotope ratio analysis and trace element analysis in two homicides. In one case, we concluded that a fatal bullet did not share a common origin with bullets in a box of ammunition containing 24 cartridges taken from suspects. Evidence in the second case included two bullets from the crime scene and 163 bullets taken from various suspects. We were able to infer that the two bullets from the crime scene did not share a common origin and that they differed from all of the bullets taken from suspects. All of the suspects' ammunition had been reloaded as was evident both from trace and isotopic analysis and, indeed, from visual inspection.     

Chronic alcoholic intoxication and the trace element composition of the hair

Chronic alcoholic intoxication was found to result in changes in trace elemental structure of human hair and mongrel white rat hair. Reliable increase of iron, zinc, copper and manganese in hair of alcoholic patients and tendency to increase iron content in rat hair were detected.     

Reassembling scattered and mixed human bones by trace element ratios

Trace metal ratios in human bones were examined to determine if there were ratios that were sufficiently consistent within an individual yet varying sufficiently from the bones of another individual so that bones in a mixed grave could be reassembled. The concentrations of 21 elements sampled at 54 places on 30 human bones in each of 5 skeletons indicated that the magnesium/zinc ratio was the most reliable and that the zinc/sodium, magnesium/sodium, and chromium/sodium ratios could be used as supplements to help reassemble human bones belonging to the same individual after all standard techniques had been used.     

Group-specific component imaging from trace material using isoelectric focussing and electroblotting

GC-subtyping was carried out on blood stains, that had been made on glass and stored under room temperature-conditions. Using isoelectric focusing in polyacrylamide gel, followed by transfer to nitrocellulose membrane by semi-dry-electroblotting and detection with enzyme-linked antibody complex the GC-detection was possible even after 64 days. Methodical problems are discussed.     

DNA profiles from biological trace material contained in underwear and toothbrushes

There are special cases where it is extremely difficult to find a close relative for obtaining reference samples, such as in adoption cases or foreigners without relatives in the country. In these cases, it is possible to use personal objects from the missing person. We developed a protocol for obtaining DNA profiles from toothbrushes and underwear and evaluated two DNA extraction methods (Silica and magnetic particles), comparing the DNA quantity and the quality of the obtained profiles. Results showed that for underwear, silica in suspension recovered higher DNA quantity but magnetic particles (PrepFiler®) generated more complete profiles. For toothbrushes PrepFiler® recovered a higher DNA quantity and generated more complete DNA profiles. Statistical analyses showed there were no significant differences between both methods. Higher DNA quantities were recovered from underwear samples, however toothbrushes generated higher quality in DNA profiles, without obtaining mixed profiles, concluding that toothbrushes are a better item than underwear. Considering that silica in suspension method is three-times cheaper than PrepFiler®, we propose it is possible to successfully obtain DNA profiles from personal objects using a low-cost DNA extract method.     

Metalloligand homeostasis: molecular basis of iatrogenic and technogenic trace element deficiency

It is well known that a toxic effect of some medicines is the result of their in vivo interactions with trace elements leading to disturbance of trace element balance in the living body. The Mossbauer spectrometry technique has been used for toxicochemical evaluation of iron-bearing medicines. This method can be used in forensic toxicology. We studied composition of trace elements in the hair of children living in Macedonia: in polluted territory (the town of Veles, the study group) versus in unpolluted one (Ivankovci village, the control group). AES-ICP and ICP-MS techniques were used. We discovered that the hair of children living in the polluted territory contain significantly elevated concentrations of Pb (in 43% cases), Hg, Ni (14%), Cd (21%), Cu (16%), Sn, As, Na, Se and subnormal concentrations of Mg (in 51% cases), Mn, Cr and Li.     

Recovery and evaluation by cytologic techniques of trace material retained on bullets

Fragments of tissue, intermediate targets, and debris related to firing are embedded in the fine striations and deforming edges of bullets. Because most of these fragments are too small to visualize and process as histologic sections, this material is usually washed away when the projectiles are cleaned following removal at autopsy. By preserving the rinsing material that results from routine cleaning of projectiles, it may be possible to evaluate adherent material from the bullet by cytologic techniques, including filter preparations, cell blocks, and smears of macroscopic tissue fragments. Bullet-wash cytology produced cellular elements, tissue fragments, and inert material from intermediate targets. Different tissue elements could be documented with a given projectile; this information could be utilized to document the path of a bullet through the body or intermediate target. This initial study suggests that low- and high-velocity projectiles produce different types of tissue debris, with much more fragmentation and scarcity of cellular components in the high-velocity rounds. Inert material, resulting from intermediate targets, such as clothing, as well as gunshot residue on the bullet or debris from the barrel could be distinguished on preparations. There was a difference in tissue representation of adherent material on the bullet; connective tissue, mesothelial coverings, and fragments from organs with higher elastic and cohesive properties were seen with much greater frequency on the filters than were loosely cohesive and friable organs such as liver and spleen. The cytologic preparations from projectile washings reflect both the path taken by the bullet and the ballistic damage to the organs. Thus, the cytologic evaluation of bullet washings may be useful in the incorporation of gunshot wound evaluation to support documentation of the trajectory of the projectile.     

Recovery and evaluation of trace material from wound edges in traumatic injury site

A small wound found on the ear of a homicide victim was inflicted by either a knife or a sharp fragment of ceramic. To test the potential usefulness of cytologic examination of wound edges for fragments of inert material from the assault weapon, the wound was rinsed and cytologic filters were prepared from the retained rinsing material. The particulate matter present on filters included microscopic fragments of crockery admixed with blood and other tissue components. This observation supported other physical evidence that the wound was caused by the sharp edge of a ceramic crock rather than by the knife. This case demonstrates the potential usefulness of cytologic examination of wound edges.     

Identification of cremains using X-ray diffraction spectroscopy and a comparison to trace element analysis

The ability to distinguish human cremains from filler materials can be important in a variety of situations, the most notorious recent example being the Tri-State Crematorium incident. However, the majority of the papers in the recent literature present methods that rely on trace or minor element analysis, usually followed by a statistical or variable cluster analysis, to determine attribution. This approach is inherently risky, as there is significant natural variation in the trace and minor element body burdens within the human population and no real baseline for comparison. Bones and teeth are a form of calcium phosphate that is part of the mineral group apatite, often referred to as bioapatite. X-ray diffraction (XRD) spectroscopy is a technique that is used to identify minerals by their crystalline structures rather than their elemental composition. The members of the mineral group apatite have a highly flexible hexagonal (6/m) structure that is able to incorporate small amounts of a wide variety of elements. However, its structure, and therefore its X-ray diffraction pattern, is distinct from the crystalline structures of all of the commonly reported filler materials, most of which are composed of some combination of Portland cement, limestone aggregate and quartz sand. XRD has several advantages over other analytical techniques for the identification of cremains. It is non-destructive, requires relatively small amounts of material, is unaffected by the elemental variations found in bioapatite, and can be used to semi-quantify the components of a mixture, thus determining the relative level of contamination of a sample. This paper presents the results of X-ray diffraction spectroscopy analysis of human cremains and a variety of common filler materials.     

An estimation of the post-mortem interval in human skeletal remains: a radionuclide and trace element approach

Estimation of the post-mortem interval remains a contentious issue, with forensic pathologists often relying upon the recognition of morphological changes.A radionuclide approach has often been suggested in the literature, although limitations have prevented its application, most notably those of diagenesis. Within this pilot study, we show for the first time that there is a correlation between certain radionuclide content and time since death.A larger study is proposed to confirm these findings and possibly provide a calibration against which bones uncovered can be dated.