Representative drug sampling: sample size calculations revisited

Calculating the required number of samples to be tested from a consignment of pills suspected of containing drugs can be performed from a Bayesian perspective. Procedures in literature are based on the outstanding work of Aitken. However, in the mathematical treatment of the problem, the limitedness of the consignment is not systematically used. The current Technical Note addresses this problem. A suitable prior distribution for the number of positive pills is derived, being a betabinomial distribution with the consignment size as one of the parameters. A hypergeometric likelihood is used, as sampling generally proceeds without replacement. The betabinomial posterior distribution is mathematically identical to the predictive distribution as reported elsewhere. The currently used large consignment approximation can be derived from the betabinomial posterior, but the quality is not optimal when compared to the exact betabinomial-based results. A new approximation is derived, with better properties, as illustrated in some examples.     

Discriminant function analysis for sex assessment in pelvic girdle bones: sample from the contemporary Mexican population

Sex assessment of skeletal remains plays an important role in forensic anthropology. The pelvic bones are the most studied part of the postcranial skeleton for the assessment of sex. It is evident that a population-specific approach improves rates of accuracy within the group. The present study proposes a discriminant function method for the sex assessment of skeletal remains from a contemporary Mexican population. A total of 146 adult human pelvic bones (61 females and 85 males) from the skeletal series pertaining to the National Autonomous University of Mexico were evaluated. Twenty-four direct metrical parameters of coxal and sacral bones were measured and subsequently, sides and sex differences were evaluated, applying a stepwise discriminant function analysis. Coxal and sacra functions achieved accuracies of 99% and 87%, respectively. These analyses follow a population-specific approach; nevertheless, we consider that our results are applicable to any other Hispanic samples for purposes of forensic human identification.     

Study of losses of volatile compounds from dynamites. Investigation of cross-contamination between dynamites stored in polyethylene bags

The purpose of this work was to study the appropriateness of polyethylene bags for the preservation of explosive specimens. To this end, specimens of two types of dynamites, Goma-2 EC, containing nitroglycol (EGDN) and dinitrotoluene (DNT), and Goma-2 ECO, containing only EGDN, were placed individually inside bags and introduced into hermetically sealed glass jars, which were stored for a period of time. Losses of volatile compounds were studied by headspace analysis using gas chromatography coupled to mass spectrometry (GC-MS). The cross-contamination between dynamites was studied by using high performance liquid chromatography with mass spectrometry (HPLC-MS) to analyse the extracts obtained after a sequential solvent extraction of these specimens. Polyethylene bags permit the loss of volatile compounds since EGDN and DNT were detected in the headspaces of the jars. Moreover, cross-contamination between dynamites was also demonstrated since DNT content decreased in the dynamite containing this compound and increased in the dynamite that had not contained it.     

Elemental analysis of glass by laser ablation inductively coupled plasma optical emission spectrometry (LA-ICP-OES)

The elemental analysis of glass evidence has been established as a powerful discrimination tool for forensic analysts. Laser ablation inductively coupled plasma optical emission spectrometry (LA-ICP-OES) has been compared to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and energy dispersive micro X-ray fluorescence spectroscopy (μXRF/EDS) as competing instrumentation for the elemental analysis of glass. The development of a method for the forensic analysis of glass coupling laser ablation to ICP-OES is presented for the first time. LA-ICP-OES has demonstrated comparable analytical performance to LA-ICP-MS based on the use of the element menu, Al (Al I 396.15 nm), Ba (Ba II 455.40 nm), Ca (Ca II 315.88 nm), Fe (Fe II 238.20 nm), Li (Li I 670.78 nm), Mg (Mg I 285.21 nm), Sr (Sr II 407.77 nm), Ti (Ti II 368.51 nm), and Zr (Zr II 343.82 nm). The relevant figures of merit, such as precision, accuracy and sensitivity, are presented and compared to LA-ICP-MS. A set of 41 glass samples was used to assess the discrimination power of the LA-ICP-OES method in comparison to other elemental analysis techniques. This sample set consisted of several vehicle glass samples that originated from the same source (inside and outside windshield panes) and several glass samples that originated from different vehicles. Different match criteria were used and compared to determine the potential for Type I and Type II errors. It was determined that broader match criteria is more applicable to the forensic comparison of glass analysis because it can reduce the affect that micro-heterogeneity inherent in the glass fragments and a less than ideal sampling strategy can have on the interpretation of the results. Based on the test set reported here, a plus or minus four standard deviation (± 4s) match criterion yielded the lowest possibility of Type I and Type II errors. The developed LA-ICP-OES method has been shown to perform similarly to LA-ICP-MS in the discrimination among different sources of glass while offering the advantages of a lower cost of acquisition and operation of analytical instrumentation making ICP-OES a possible alternative elemental analysis method for the forensic laboratory.     

Volition versus feasibility: state aid when aid is looked upon favourably: the broadband example

The European Commission published on September 30, 2009, Guidelines for the application of State aid rules in relation to rapid deployment of broadband networks. These Guidelines are applicable to two markets that are connected, although somewhat different. In ??traditional?? or ??first generation?? broadband networks, public intervention mainly relates to rural communities or areas which are economically underdeveloped. Therefore, a corrective nature of the aid is maintained. However, the Guidelines are also applied to accelerate the deployment of next-generation access (NGA) networks, which implies a driving conception of State aid, as this is an emerging market and there are relatively few Europeans who have access to these networks. The analysis of these Guidelines thus seems relevant due to its novelty and, particularly, to the results that it can bring.     

Public Reason Between Ethics and Law

Rawls says that public reason is the reason of the citizens of a democratic state and takes the Supreme Court in the USA as the exemplar of public reason. It differs from non public reason, which is used e.g., in universities and academic institutions. Rawls contrasts with Kant, which opposes the public reason of the scholar??or the philosopher??, who speaks before the world, to the private reason of state or church officials. The later, once they accept an authority, cannot think by themselves (selbst denken). A closer examination shows that Rawls is not so far from Kant as it seems, because he takes the constitutional judges not as they are, but as they should be. However Rawls still apparently refuses Kant??s unity of reason. Further investigation of the relations between ethical reason, democratic reason and legal reason is needed. Democratic reason is tantamount both to public reason and to legal reason in a modern constitutional state. It is a requirement of ethics but still not identical with ethical reason, since it is possible to accept democratic reason and to argue against it from an ethical point of view. There is just one good way of reasoning, in spite of the constraints that the sources of law and the rules of procedure impose on legal reasoning, compared with ethics. Such constraints are based on the democratic principle, which is again based on ethical reason, which at last both grounds and limits the constraints that law imposes on reason.     

Trust in the proposed EU regulation on trust services?

A few months after ICRI's 20th anniversary conference the European Commission adopted on 4 June 2012 a draft regulation “on electronic identification and trusted services for electronic transactions in the internal market”. The proposed legal framework is intended to give legal effect and mutual recognition to trust services including enhancing current rules on e-signatures and providing a legal framework for electronic seals, time stamping, electronic document acceptability, electronic delivery and website authentication. Yet, this draft Regulation provokes many questions with regard to the implicit “trust” concept on which it is based. Starting from their experience in the EU FP7 uTRUSTit project (Usable Trust in the Internet of Things: www.utrustit.eu) and in other ICRI research projects, Jos Dumortier and Niels Vandezande have analyzed the proposed legislative text of the European Commission and wrote a few critical observations. Although obviously not presented at the conference in November 2011, it seemed worthwhile to add this contribution to its proceedings.     

A stochastic model of the processes in PCR based amplification of STR DNA in forensic applications

In forensic DNA profiling use is made of the well-known technique of PCR. When the amount of DNA is high, generally unambiguous profiles can be obtained, but for low copy number DNA stochastic effects can play a major role. In order to shed light on these stochastic effects, we present a simple model for the amplification process. According to the model, three possible things can happen to an individual single DNA strand in each complete cycle: successful amplification, no amplification, or amplification with the introduction of stutter. The model is developed in mathematical terms using a recursive approach: given the numbers of chains at a given cycle, the numbers in the next can be described using a multinomial probability distribution. A full set of recursive relations is derived for the expectations and (co)variances of the number of amplicon chains with no, 1 or 2 stutters. The exact mathematical solutions of this set are given, revealing the development of the expectations and (co)variances as function of the cycle number. The equations reveal that the expected number of amplicon chains without stutter grows exponentially with the cycle number, but for the chains with stutter the relation is more complex. The relative standard deviation on the numbers of chains (coefficient of variation) is inversely proportional to the square root of the expected number of DNA strands entering the amplification. As such, for high copy number DNA the stochastic effects can be ignored, but they play an important role at low concentrations. For the allelic peak, the coefficient of variation rapidly stabilizes after a few cycles, but for the chains with stutter the decrease is more slowly. Further, the ratio of the expected intensity of the stutter peak over that of the allelic peak increases linearly with the number of cycles. Stochastic models, like the one developed in the current paper, can be important in further developing interpretation rules in a Bayesian context.     

Trichophyton Mentagrophytes Perforates Hair of Adult Corpses in the Gaseous Period*

Abstract: Despite the substantial literature on mycology, there are still limited reports of the interaction between fungi and human hosts in the postmortem period. Thus, the main goal of this study was to investigate the in vitro perforation test using Trichophyton mentagrophytes on hair from adult corpses in the postmortem period (gaseous period). The protocol was carried out with positive (prepubescent children’s hair) and negative controls (healthy adult hair) as well. One strain of Trichophyton rubrum was also used as a negative perforation control. Perforations were found in all the hair samples from corpses and prepubescent children after 12–14 days exposure to T. mentagrophytes and were absent in the hair samples of healthy adults. Furthermore, hair perforation was not observed with T. rubrum. Our preliminary findings suggest the use of T. mentagrophytes as a potential marker of the death interval in forensic science.