Windows of Opportunity: Window Subseries Empirical Variance Estimators in International Relations

We show that temporal, spatial, and dyadic dependencies amongobservations complicate the estimation of covariance structuresin panel databases. Ignoring these dependencies results in covarianceestimates that are often too small and inferences that may bemore confident about empirical patterns than is justified bythe data. In this article, we detail the development of a nonparametricapproach, window subseries empirical variance estimators (WSEV),that can more fully capture the impact of these dependencieson the covariance structure. We illustrate this approach ina simulation as well as with a statistical model of internationalconflict similar to many applications in the international relationsliterature.     

Compositional variation in bullet lead manufacture

The concentrations of antimony, copper, tin, arsenic, silver, bismuth, and cadmium in lead alloys produced by two smelters and one ammunition manufacturer were determined using inductively coupled plasma-atomic emission spectrometry. These element concentrations were used to measure the variations in composition of lead products that result from various processes involved in the manufacture of lead projectiles. In general, when a pot containing molten lead is used to cast a number of objects, these objects are similar, although not necessarily analytically indistinguishable in their elemental compositions. In each subsequent step in the processing of lead at the smelter and at the ammunition manufacturer, the size of an individual homogeneous melt of lead decreases as more distinct compositions are formed as a result of remelting and mixing of sources, including lead scrap. The ammunition manufacturer in this study produced at least 10 compositionally distinguishable groups of bullet wire in a 19.7-h period. The largest group could potentially be used to produce a maximum of 1.3 million compositionally indistinguishable 40 grain bullets.     

Surface sterilization of a maggot using bleach does not interfere with mitochondrial DNA analysis of crop contents

Mitochondrial DNA analysis of a maggot crop can identify the corpse a maggot has been feeding on. Analysis of the crop could be useful in a criminal investigation if maggots are found at a suspected crime scene in the absence of a body, or if there is a question of whether a maggot used in postmortem interval estimations moved onto the corpse from another food source. Such analysis can also resolve a chain of custody dispute if it has been suggested that larval samples have been switched. When recovering DNA from a maggot crop, the analyst must be careful to avoid external contamination. We investigated the effects of three simple wash methods developed to reduce external contamination. Maggots raised on pig liver and intentionally contaminated with cow blood were washed using water, 20% bleach, or a solution containing the enzyme DNase. Only washing the maggots in 20% bleach reduced the amount of vertebrate DNA amplified from the maggots' exteriors. No wash method affected the ability to recover DNA from the maggot crops.     

Analysis of ionic ratios in myocardial tissue and their relation to cardiac damage

The authors evaluated the usefulness of the postmortem biochemical analysis of ionic ratios in different parts of the heart and their relation to cardiac damage caused by chest trauma, as observed by anatomopathologic study. Fifty-nine 59 cases were studied, selected from routine necropsies, and samples were taken from different sites of cardiac tissue. The cause of death was trauma in 40 cases and nontraumatic causes in 19 cases. The object of this study was to analyze the levels of Na+, K+, Ca+2, Mg+2, and Zn+2 in different zones of the heart, and the relationship between intracellular and extracellular ion ratios and the different causes of death and any anatomopathologic alterations observed. The biochemical tests revealed a possible relation between the ionic values and cause of death. Alterations in cell membrane permeability and corresponding modification of the ionic ratios were produced earlier than histologic alterations, which need longer to establish themselves whether or not they follow a traumatic process.     

Diagnostic problems associated with cadaveric trauma from animal activity

Analysis of a series of deaths between 1986 and 2001 resulting from natural disease, accidents, suicides, and homicide, where postmortem animal activity had traumatized bodies, was undertaken at the Forensic Science Center in Adelaide to demonstrate the range of lesions that may occur and problems in interpretation that result. Tissue damage had been caused by a variety of animals, including fly larvae, ants, birds, dogs, rodents, sea lice, and sharks. Postmortem animal activity had disguised injuries, modified wounds, and created the appearances of inflicted injury. Problems with identification occurred after postmortem facial trauma, and loss of organ parenchyma had interfered with, or precluded, the precise determination of the manner of death in some cases. Specific kinds of tissue and organ damage may occur after death, necessitating careful assessment of lesions in a search for characteristic features of animal activity. The pattern of lesions may enable identification of the particular species of animal involved.     

Extension of the color suite available for chemical enhancement of fingerprints in blood

The use of ortho- and para-phenylenediamine (OPD & PPD respectively) for the enhancement of fingerprints in blood has been investigated. Optimal pH conditions and H2O2 concentrations have been determined using UV/Vis spectroscopy. Both OPD and PPD are effective and less hazardous alternatives to the presently used 3,3'-diaminobenzidine (DAB) for the development of blood fingerprints, especially on porous surfaces. The orange color of OPD and the purple color of PPD offer alternative colors to the brown color of DAB and the light green color of ABTS for standing out against particular backgrounds. Both OPD and PPD can be used after ninhydrin treatment, but the reverse is not the case.     

Interpretation of glass composition measurements: the effects of match criteria on discrimination capability

The concentrations of ten elements in 209 unrelated glass specimens received as evidence were used to assess the frequencies of errors of false association (Type II errors) using several comparison criteria at specified significance levels (Type I errors). Pairwise comparisons of the samples using either the equal-variance t-test or Welch's modification (unequal variances) result in a small number of errors of false association, even when adjusting the significance level (Bonferroni correction) for multivariate comparisons. At the 95% confidence level (overall Type I error of 0.05, or individual element comparison error of 0.005), only two Type II errors are made in 21736 comparisons (0.009%) when using the equal-variance t-test for comparison of sample means. In this study, the range overlap test using three replicate measurements per specimen results in no errors of false association. Most specimen pairs in this data set are readily discriminated either by differences in the concentrations of several elements or by an extremely large difference in the concentrations of one or more element.     

Deaths associated with liposuction: case reports and review of the literature

Tumescent liposuction is a common cosmetic procedure that is performed as an outpatient service in physician's offices and is largely believed to be safe. The protuberant areas of the body containing the undesirable fat deposits are injected with normal saline containing lidocaine and epinephrine for pain control and hemostasis, and the waterlogged cells are suctioned out via cannula through a small incision. We recently encountered three cases in which deaths were attributed to this procedure. Two showed fat embolization in the lung and one died from fluid overload. The osmium tetroxide post-fixed lung sections showed fat emboli in the interstitial capillaries and arterioles. We reviewed the recent literature and found that pulmonary thromboemboli, fat embolization, fluid overload, and lidocaine and epinephrine intoxication are found at autopsy in many cases. Forensic pathologists responsible for determining the cause and manner of death should become familiar with the postmortem findings and risks of liposuction therapy and communicate them to their clinical colleagues and communities.     

Comparison of the elemental composition of office document paper: evidence in a homicide case

Fraudulent substitution of a page within a multiple page document such as a will or business contract, the counterfeit manufacture of paper banknotes, and linking ransom or extortion notes have all been the focus of criminal investigations at one time or another. In a recent homicide investigation, document examiners were requested to compare a threatening letter received by a business partner of the deceased with paper samples seized under warrant from a suspect's house. Through a quantitative elemental analysis of the concentrations of nine elements (Na, Mg, Al, Mn, Sr, Y, Ba, La, and Ce) within the questioned and specimen documents, determined by inductively coupled plasma-mass spectrometry (ICP-MS), it was concluded that (i) the paper of the threatening letter originated from a different source to that of the paper seized from the suspect's house and (ii) all six pages of paper seized from the suspect's house originated from the same source. This discrimination of paper is presented as both a statistical t-test analysis (99.9% confidence limit) as well as construction of an elemental fingerprint for individual replicates within the questioned and specimen sample populations. This is the first reported use of the comparison of the elemental composition of document paper, determined by ICP-MS, to assist in a criminal investigation.