Learning about Bayesian networks for forensic interpretation: an example based on the 'the problem of multiple propositions'

Both, Bayesian networks and probabilistic evaluation are gaining more and more widespread use within many professional branches, including forensic science. Notwithstanding, they constitute subtle topics with definitional details that require careful study. While many sophisticated developments of probabilistic approaches to evaluation of forensic findings may readily be found in published literature, there remains a gap with respect to writings that focus on foundational aspects and on how these may be acquired by interested scientists new to these topics. This paper takes this as a starting point to report on the learning about Bayesian networks for likelihood ratio based, probabilistic inference procedures in a class of master students in forensic science. The presentation uses an example that relies on a casework scenario drawn from published literature, involving a questioned signature. A complicating aspect of that case study - proposed to students in a teaching scenario - is due to the need of considering multiple competing propositions, which is an outset that may not readily be approached within a likelihood ratio based framework without drawing attention to some additional technical details. Using generic Bayesian networks fragments from existing literature on the topic, course participants were able to track the probabilistic underpinnings of the proposed scenario correctly both in terms of likelihood ratios and of posterior probabilities. In addition, further study of the example by students allowed them to derive an alternative Bayesian network structure with a computational output that is equivalent to existing probabilistic solutions. This practical experience underlines the potential of Bayesian networks to support and clarify foundational principles of probabilistic procedures for forensic evaluation.     

Monitoring compliance to therapy during addiction treatments by means of hair analysis for drugs and drug metabolites using capillary zone electrophoresis coupled to time-of-flight mass spectrometry

Capillary electrophoresis coupled to time-of-flight mass spectrometry was used in the present work for the determination of therapeutic and abused drugs and their metabolites in the hair of subjects undergoing addiction treatments, in order to monitor their compliance to therapy. For this purpose a rapid, qualitative drug screening method was adopted based on capillary electrophoresis hyphenated with time-of-flight mass spectrometry, which had earlier been developed and validated for the forensic-toxicological analysis of hair, limitedly to illicit/abused drugs [1]. Sampling of hair was carried out in order to refer to a time window of about two months from the date of sampling (i.e. 2cm ca. from cortex). A single extraction procedure was applied, allowing the determination in the hair matrix of "drugs of abuse" referred to the past abuses, and therapeutic drugs prescribed in the detoxification program as well as their metabolites. Analyte identification was based on accurate mass measurements and comparison of isotope patterns, providing the most likely matching between accurate mass value and elemental formula. Small molecules (<500Da) of forensic and toxicological interest could be identified unambiguously using mass spectrometric conditions tailored to meet a mass accuracy ≤5ppm. In the present study, the proposed approach proved suitable for the rapid broad spectrum screening of hair samples, although needing further confirmation of results by using fragmentation mass spectrometry.     

Palynology and mycology as biological evidence in a homicide case

Criminal cases are studied from several disciplines to link a suspect with a criminal act. In this case, a man was reported missing in a coastal area in Buenos Aires Province, Argentina. The victim's relatives pointed to a possible suspect, and the local police carried out the investigation. We contributed to this research by applying palynological and mycological techniques. Palynomorphs and fungal spores offer valuable trace evidence, as they can be easily transferred between objects and crime scenes due to their minute size and persist on them for a long time. The victim was found 25 days later, lying on sandy soil, which partially covered the body, 35 km from where the suspect was arrested. Comparative samples were collected from the crime scene and the suspect's home and belongings (clothes, footwear, and seized vehicle). The palynological associations obtained from the crime scene and the defendant's belongings were dominated by diatoms and acritarchs (Acantomorphitae), all elements of marine origin, and a high CFU number of Bipolaris cynodontis, which allowed the defendant's clothing to be related to the place of corpse discovery. Soil from the defendant's home had an entirely continental composition, and the fungal biota was characteristic of prairie areas which were different from those of the crime scene.     

Standing for the client: on the interactional becoming of the criminal defence attorney1

In this essay, I explore the meaning of the legal profession (the defence attorney). I carry out my investigation in the interactional register. I suggest that we examine the profession of defence attorney as a professional identity in becoming. I localize the event of becoming in the first attorney-client interview. I propose that it is during the first encounter that the attorney comes to stand for the client as a legal counsel. I further propose that the analogy of ‘standing for’ be accessed empirically through an analysis of a recorded episode from the first attorney-client conference. For my methods I use a combination of frame analysis and conversation analysis. The two analyses show how the attorney becomes to stand for the client as a legal figure moulded in a series of interactional moves. By reformulating and reframing the ordinary talk that is introduced as an entry mode into an institutional relationship, the attorney and the client alter their discursive positions until the attorney assumes his professional identity, that is, becomes to stand for the client in legal action.     

Patent-Secret Mix in Complex Product Firms

Different protection mechanisms may be employed at the sametime when an innovation is comprised of separately protectablecomponents. If patents and trade secrets can be mixed in protectingsingle innovations, a strengthening in patent breadth may inducea lower level of patenting, as innovators are more prone torely on secrecy.     

中国参与国际气候谈判的立场演变

中国参与国际气候谈判的历程是同期中国整体外交的缩影,其立场演变经历了被动却积极参与、谨慎保守参与以及活跃开放参与三个发展阶段,且每个阶段气候谈判立场的演变都有着内在的决定因素。气候外交作为中国整体外交的一部分,深刻反映了中国外交日趋成熟的发展进程。