Improved estimation of postmortem interval based on differential behaviour of vitreous potassium and hypoxantine in death by hanging

Many formulae are available to estimate the relation between the potassium ([K+]) and hypoxantine ([Hx]) concentration in the vitreous humour and the postmortem interval (PMI). Typically these have been based on a correlation test and linear regression using the postmortal interval as the independent variable and [K+] or [Hx] as the dependent variable in order to estimate the confidence interval. However, a recent study has shown that a more precise measurement of PMI can be obtained if [K+] is used as the independent variable. The regression lines obtained from the most recent deceased subjects with forensic relevance received for autopsy in the Institute of Legal Medicine are [K+] = 5.589 + 0.174PMI and [Hx] = 26.459 + 3.017PMI, by changing the variables, we obtain PMI=3.967[K+] - 19.186 (R2 = 0.688, P < 0.001) and PMI = 0.172 [Hx] + 0.170 (R2 = 0.518, P < 0.001). In this paper we propose the cause of death as an extra factor which modifies the relationship and gives even greater precision in estimating PMI. In cases of death by hanging the results are considerably improved with [K+] = 5.224 + 0.225PMI and [Hx] = 15.161+4.957PMI, respectively, and consequently, PMI = 3.631[K+] - 17.334 (R2 = 0.818, P< 0.001) and PMI = 0.153[Hx] - 0.368 (R2 = 0.757, P < 0.001): the slope is less and the precision is obviously enhanced.     

Progress Toward the Determination of Correct Classification Rates in Fire Debris Analysis II: Utilizing Soft Independent Modeling of Class Analogy (SIMCA)

A multistep classification scheme was used to detect and classify ignitable liquid residues in fire debris into the classes defined by the ASTM E1618‐10 standard method. The total ion spectra (TIS) of the samples were classified by soft independent modeling of class analogy (SIMCA) with cross‐validation and tested on fire debris. For detection of ignitable liquid residue, the true‐positive rate was 94.2% for cross‐validation and 79.1% for fire debris, with false‐positive rates of 5.1% and 8.9%, respectively. Evaluation of SIMCA classifications for fire debris relative to a reviewer's examination led to an increase in the true‐positive rate to 95.1%; however, the false‐positive rate also increased to 15.0%. The correct classification rates for assigning ignitable liquid residues into ASTM E1618‐10 classes were generally in the range of 80–90%, with the exception of gasoline samples, which were incorrectly classified as aromatic solvents following evaporative weathering in fire debris.     

Establishing Tobacco Origin from Pollen Identification: An Approach to Resolving the Debate

Previous research into pollen content of tobacco resulted in a debate. We address this debate and determine that pollen analysis may be able to assist with identifying geographical origin of tobacco. However, the value of any results should be assessed on a case‐by‐case regional basis until sufficient database information is available for an objective interpretation to be undertaken on a global basis. As a first step toward developing comparative data for South America, we analyzed a tobacco sample from Brazil in an effort to identify signature taxa from the state of Minas Gerais. We also assessed the role of honey additives to tobacco to assess this issue. Comparing the data to previously published data, we conclude that pollen signatures can distinguish broad geographic areas. We conclude that this forensic interpretation framework needs to be developed in context of the National Academy of Sciences recommendations for tightening methods in forensic science.     

Extending the “voting with the feet” proposition: the impact of local economic development actions on immigration across Mexican municipalities

Tiebout's “voting with the feet” proposition directs attention to the role of local authorities in delivering public services, and the implications of their decisions in people's choice of place of residence. Similarly, the bottom-up approach to economic development places a relevant role of local governments in promoting higher standards of living. By considering the latter, the former can be extended as citizens can choose a jurisdiction not only on the basis of a combination of taxes and public services but a broader mix of public goods. This paper analyses the effects of the fundamental features of the bottom-up or local economic development (LED) approach on population mobility among Mexican municipalities. This study finds significant evidence of a positive impact of LED elements on immigration during the period between 1990 and 2005.     

Unsuspected hereditary hemochromatosis at forensic autopsy: its presentation, confirmation, and implications

Hereditary hemochromatosis (HH) is one of the most common genetic disorders and may present clinically in a variety of ways. The most common presentation is micronodular cirrhosis with possible associated diabetes. However, HH may also present with cardiac dysfunction and sudden death. The confirmation of unsuspected HH at autopsy is complicated by the growing number of genetic abnormalities, which are not detected by current commercial genetic testing for C282Y and H63D mutations. Consequently, quantitative liver iron studies on fresh or paraffin embedded liver is recommended in confirming HH. The importance of detection and confirmation of HH cannot be overemphasized given the need to screen surviving family members in preventing organ damage of asymptomatic individuals. We present a case of a 38-year-old white woman with micronodular cirrhosis secondary to unsuspected HH that was confirmed by a quantitative liver iron study. The possible presentation of cardiac sudden death from HH, confirmation issues and implications of a HH diagnosis for surviving family members are also discussed.     

Analysis of active ricin and castor bean proteins in a ricin preparation, castor bean extract, and surface swabs from a public health investigation

In late February 2008, law enforcement officials in Las Vegas, Nevada, discovered in a hotel room, a copy of The Anarchist Cookbook, suspected castor beans and a "white powder" thought to be a preparation of ricin. Ricin is a deadly toxin from the seed of the castor bean plant (Ricinus communis). The United States regulates the possession, use, and transfer of ricin and it is the only substance considered a warfare agent in both the Chemical and the Biological Weapons Conventions. Six samples obtained from the hotel room were analyzed by laboratories at the Centers for Disease Control and Prevention using a panel of biological and mass spectrometric assays. The biological assays (real time-PCR, time resolved fluorescence and cytotoxicity) provided presumptive evidence of active ricin in each of the samples. This initial screen was followed by an in-depth analysis using a novel, state-of-the-art mass spectrometry-based ricin functional assay and high sensitivity tandem mass spectrometry for protein identification. Mass spectrometric analysis positively identified ricin and confirmed that in each of the samples it was enzymatically active. The tandem mass spectrometry analysis used here is the most selective method available to detect ricin toxin. In each sample, ricin was unequivocally identified along with other R. communis plant proteins, including the highly homologous protein RCA120. Although database searches using tandem mass spectra acquired from the samples indicated that additional controlled substances were not present in these samples, the mass spectrometric results did provide extensive detail about the sample contents. To the best of our knowledge following a review of the available literature, this report describes the most detailed analysis of a white powder for a public health or forensic investigation involving ricin.