Bloodstains on Leather: Examination of False Negatives in Presumptive Test and Human Hemoglobin Test

Presumptive tests for blood are very simple and sensitive tests used in the search for evidence. They also provide initial information on the nature of stains. A second test can confirm their nature. However, these tests can present false–negative results for different reasons. Some of those reasons have been studied, while others, those caused by the substrate material that contains the stain, are less well known. This work studies the effect of one component of a leather substrate—quebracho extract—on presumptive and human hemoglobin blood tests. Assays were performed using samples of blood dilutions contaminated with quebracho extract and others formed on a substrate containing the contaminant. Results show an undoubted interference that causes false negatives and even visible to the naked eye stains and also indicate that some tests (phenolphthalein) are more affected than others. Examiners should be taken into account when working on this kind of substrates.     

One or two arenas? The break-up between national and regional elections

ABSTRACT

This paper shows that the role of national electoral dynamics on regional elections is highly mediated by institutional and electoral constraints at the regional level. Using data on statewide parties’ electoral competition in regional and national elections in Spain and Italy, results show that the contamination of regional elections is lower in regions where decentralization has travelled further and where strong regionalist parties dominate electoral competition. The paper also shows that these two channels -more regional authority and more regionalist competition- shape the regional manifestos of statewide parties by increasing their pro-regional positions. These findings represent a contribution to a better understanding of the extent to which regional elections are a separate electoral arena from the national one.     

Chemistry in crime investigation: sodium percarbonate effects on bloodstains detection

Chemistry plays a leading role in crime investigation. In the study of bloodstains, chemical reactions provide the means for the detection. All these procedures have been thoroughly studied. However, recently, a new source of error has been found: washing stains with "active oxygen" detergents abrogates presumptive and human hemoglobin tests for bloodstains (although visible). The aim of this investigation was to evaluate the ability of pure sodium percarbonate-main component of detergents-to abrogate presumptive and human hemoglobin tests. Then, a solution to this problem could be found. The results demonstrate that pure sodium percarbonate-itself-is able to abrogate all tests, as well as the different degrees to which each of them is affected by the product. Consequently, faced with a stain of bloody appearance, even the preliminary tests are negative; it is advisable to analyze the DNA. Otherwise, the opportunity of obtaining valuable information is lost.     

High resolution Y chromosome typing: 19 STRs amplified in three multiplex reactions

Nineteen Y-specific short tandem repeat (STR) loci have been amplified in 768 samples from the Iberian Peninsula in order to evaluate their usefulness in forensic casework. Two previously published multiplex reactions by Thomas et al. [Hum. Genet. 6 (1999) 577] (MS1, modified here: DYS19, DYS388, DYS390, DYS391, DYS392 and DYS393) and by Ayub et al. [Nucl. Acids Res. 28 (2000) e8] (CTS: DYS434, DYS435, DYS436, DYS437, DYS438 and DYS439) plus a novel one reported here (EBF: DYS385, DYS389, DYS460, DYS461, DYS462 and amelogenin) have been used. DYS385, DYS439 and DYS391 were the most informative loci with allele diversities of 0.7997, 0.6683 and 0.5940, respectively. A total of 635 different haplotypes were observed, of which 573 (90.24%) were found in single individuals. The overall haplotype diversity was 0.9988 and that obtained by each multiplex system was 0.9812 for EBF, 0.9292 for MS1 and 0.9089 for CTS.     

Solving underwater crimes: Development of latent prints made on submerged objects

Underwater crime scenes always present a challenge for forensic researchers, as the destructive effect of water considerably complicates the chances of recovering material of evidential value. The aim of this study is to tackle the problem of developing marks that have been left on submerged objects. Fingermark deposition was randomly made on two surfaces — glass and plastic whilst the material was submerged under tap water and then left for one to fifteen days before drying and development. For their later development, various reagents – Black Powder, Silver Metallic Powder, Fluorescent Powder, Sudan Black (powder and solution) and Small Particle Reagent – were used and the effectiveness of each of them on this particular type of evidence was then evaluated.The results show the possibility of obtaining good quality developed marks, even under such adverse circumstances. Further and wider research should, therefore, be undertaken in which other variables are introduced such as different substrates, other types of liquids, and environmental or time factors.     

Are Preferences for Fiscal Discipline Endogenous

Differences in voters' fiscal preferencesare examined taking advantage of theexceptional Swiss institutional setting.Empirical evidence suggests thatpreferences are determined by strictlycultural patterns (cultural area measuredby language). Thus, fiscal preferences canbe considered as being largely exogenous.This implies that, except for specialcases, it is not possible to find simpleproxy variables for fiscal preferences. Anad hoc index of fiscal preferencesought to be built up when the introductionof this variable is required forcomprehensive explanatory models of fiscaldiscipline or for other related studies.