Probabilistic evidential assessment of gunshot residue particle evidence (Part II) : Bayesian parameter estimation for experimental count data.

Part I of this series of articles focused on the construction of graphical probabilistic inference procedures, at various levels of detail, for assessing the evidential value of gunshot residue (GSR) particle evidence. The proposed models - in the form of Bayesian networks - address the issues of background presence of GSR particles, analytical performance (i.e., the efficiency of evidence searching and analysis procedures) and contamination. The use and practical implementation of Bayesian networks for case pre-assessment is also discussed. This paper, Part II, concentrates on Bayesian parameter estimation. This topic complements Part I in that it offers means for producing estimates useable for the numerical specification of the proposed probabilistic graphical models. Bayesian estimation procedures are given a primary focus of attention because they allow the scientist to combine (his/her) prior knowledge about the problem of interest with newly acquired experimental data. The present paper also considers further topics such as the sensitivity of the likelihood ratio due to uncertainty in parameters and the study of likelihood ratio values obtained for members of particular populations (e.g., individuals with or without exposure to GSR).

A half century retrospective study of homicide-suicide in Geneva--Switzerland: 1956-2005.

This study provides a retrospective review from the forensic files of the University Centre of Legal Medicine in Western Switzerland in Geneva, from January 1956 to December 2005. The studied homicide-suicide cases cover a period of half a century (50 years). As a rule, all police-ordered forensic examinations of violent death cases in the Canton of Geneva are conducted by the University Centre of Legal Medicine. All of the data necessary for an exhaustive retrospective study are thus readily available. During the period covered in this work, 228 homicides were perpetrated in Geneva. In 23 cases, the homicide was followed by the suicide of the aggressor. The 34 victims of these homicides (18 women, 1 man and 15 children) had either an intimate or filial relationship with the perpetrator. Most of the suicidal perpetrators were men that killed their spouses or intimate partners, with children as additional victims in some cases. Shooting was the most common means to kill, followed by stabbing. The majority of the victims and perpetrators were Swiss nationals. This retrospective study shows that in the last 50 years, homicide-suicide cases in the Canton of Geneva have been a rare and an episodic phenomena with a very variable frequency from 1 year to another.

Determination of bacterial quantity by sonication in vacum-assisted closure (VAC) foams used for treatment of chronic wounds

Background: Negative pressure wound treatment is increasingly used through a Vacuum-Assisted Closure (VAC) device in complex wound situations. For this purpose, sterile polyurethane (PU) and polyvinyl alcohol (PVA) foam dressings are fitted to the wound size and covered with an adhesive drape to create an airtight seal. Little information exists about the type and quantity of microorganisms within the foams. Therefore, we investigated VAC foams after removal from the wound using a validated method (sonication) to detect the bacterial bioburden in the foam consisting as microbial biofilms.Methods: We prospectively included VAC foams (PU and PVA, KCI, Rümlamg, Switzerland) without antibacterial additions (e.g. silver), which were removed from wounds in patients with chronic ulcers from January 2007 through December 2008. Excluded were patients with acute wound infection, necrotizing fasciitis, underlying osteomyelitis or implant. Removed foams from regular changes of dressing were aseptically placed in a container with 100 ml sterile Ringer's solution. Within 4 hours after removal, foams were sonicated for 5 min at 40 kHz (as described in NEJM 2007;357:654). The resulting sonication fluid was cultured at 37°C on aerobic blood agar plates for 5 days. Microbes were quantified as No. of colony-forming units (CFU)/ml sonication fluid and identified to the species level.Results: A total of 68 foams (38 PU and 30 PVA) from 55 patients were included in the study (median age 71 years; range 33-88 years, 57% were man). Foams were removed from the following anatomic sites: sacrum (n=29), ischium (n=18), heel (n=13), calves (n=6) and ankle (n=2). The median duration of being in place was 3 days (range, 1-8 days). In all 68 foams, bacteria were found in large quantities (median 105 CFU/ml, range 102-7 CFU/ml sonication fluid. No differences were found between PU and PVA foams. One type of organisms was found in 11 (16%), two in 17 (24%) and 3 or more in 40 (60%) foams. Gram-negative rods (Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa) were isolated in 70%, followed by Staphylococcus aureus (20%), koagulase-negative staphylococci, streptococci (8%), and enterococci (2%).Conclusion: With sonication, a high density of bacteria present in VAC foams was demonstrated after a median of 3 days. Future studies are needed to investigate whether antimicrobial-impregnated foams can reduce the bacterial load in foams and potentially improve wound healing.

Instrument for evaluating care given by undergraduate nursing students to people with wounds

OBJECTIVE The aim of this study was to present the process of construction and validation of an instrument for evaluating the care provided to people with wounds, to be used with undergraduate nursing students. METHOD Methodological study, with quantitative approach, using the Delphi technique in two rounds, the first with 30 judges and the second with 18. The analysis was made with Kappa coefficient ≥0.80, and content validity index greater than >0.80, also using the Wilcoxon test for comparison of the indices between the rounds. RESULTS It was found that of the 20 categories of the instrument, 18 presented better scores in the second Delphi round. Scores were greater in the second round in seven of the ten evaluation categories. CONCLUSION Based on the evaluation by the judges, a version of the instrument was defined with adequate indices of agreement and validity, which will be able to help in evaluating care of people with cutaneous injury given by undergraduate nursing students.

Production of Pseudomonas aeruginosa Intercellular Small Signaling Molecules in Human Burn Wounds

Pseudomonas aeruginosa has developed a complex cell-to-cell communication system that relies on low-molecular weight excreted molecules to control the production of its virulence factors. We previously characterized the transcriptional regulator MvfR, that controls a major network of acute virulence functions in P. aeruginosa through the control of its ligands, the 4-hydroxy-2-alkylquinolines (HAQs)-4-hydroxy-2-heptylquinoline (HHQ) and 3,4-dihydroxy-2-heptylquinoline (PQS). Though HHQ and PQS are produced in infected animals, their ratios differ from those in bacterial cultures. Because these molecules are critical for the potency of activation of acute virulence functions, here we investigated whether they are also produced during human P. aeruginosa acute wound infection and whether their ratio is similar to that observed in P. aeruginosa-infected mice. We found that a clinically relevant P. aeruginosa isolate produced detectable levels of HAQs with ratios of HHQ and PQS that were similar to those produced in burned and infected animals, and not resembling ratios in bacterial cultures. These molecules could be isolated from wound tissue as well as from drainage liquid. These results demonstrate for the first time that HAQs can be isolated and quantified from acute human wound infection sites and validate the relevance of previous studies conducted in mammalian models of infection.

The use of the vac in complex wounds - does it work and how?

Background: Complex wounds pose a major challenge in reconstructive and trauma surgery. Several approaches to increase the healing process have been proposed in the last decades. In this study we study the mechanism of action of the Vacuum Assisted Closure device in diabetic wounds. Methods: Full-thickness wounds were excised in diabetic mice and treated with the VAC device or its isolated components: an occlusive dressing (OD) alone, subathmospheric pressure at 125 mm Hg (Suction), and a polyurethane foam without (Foam) and with (Foamc) downward compression of approximately 125 mm Hg. The last goups were treated with either the complete VAC device (VAC) or with a silicne interface that alows fluid removel (Mepithel-VAC). The effects of the treatment modes on the wound surface were quantified by a two-dimensional immunohistochemical staging system based on vasculature, as defined by blood vessel density (CD31) and cell proliferation (defined by ki67 positivity), 7 days post wounding. Finite element modelling was used to predict wound surface deformation under dressing modes and cross sections of in situ fixed tissues were used to measure actual microstrain. Results: The foam-wound interface of the Vacuum Assisted Closure device causes significant wound stains (60%) causing a deformation of the single cell level leading to a profound upregulation of cell proliferation (4-fold) and angiogenisis (2.2-fold) compared to OD treated wounds. Polyurethane foam exposure itself causes a frather unspecific angiogenic response (Foamc, 2 - fold, Foam, 2.2 - fold) without changes of the cell proliferation rate of the wound bed. Suction alone without a specific interface does not have an effect on meassured parameters, showing similar results to untreated wounds. A perforated silicone interface caused a significant lower microdeforamtion of the wound bed correlating to changes of the wound tissues. Conclusion: The Vacuum Assisted Closure device induce significanttissue growth in diabetic wounds. The wound foam interface under suction causes profound macrodeformation that stimulates tissue growth by angiogenesis and cell proliferation. It needs to be taken in consideration that in the clinical setting different wound types may profit from different elements of this suction device.

The wound watch: an objective staging system for wounds in the diabetic (db/db) mouse model.

As in cancer biology, in wound healing there is a need for objective staging systems to decide for the best treatment and predictors of outcome. We developed in the diabetic (db/db) wound healing model, a staging system, the "wound watch," based on the quantification of angiogenesis and cell proliferation in open wounds. In chronic wounds, there is often a lack of cellular proliferation and angiogenesis that leads to impaired healing. The wound watch addresses this by quantifying the proliferative phase of wound healing in two dimensions (cellular division and angiogenesis). The results are plotted in a two-dimensional graph to monitor the course of healing and compare the response to different treatments.

16-OR: Investigation of Sharp Trauma and Gunshot Cases Using Post-mortem CT-Angiography

Investigation of violent death, especially cases of sharp trauma and gunshot, is an important part of medico-legal investigations. Beside the execution of a conventional autopsy, the performance of a post-mortem Multi-Detector Computed Tomography (MDCT)-scan has become a highly appreciated tool. In order to investigate also the vascular system, post-mortem CT-angiography has been introduced. The most studied and widespread technique is the Multi-phase post-mortem CT-angiography (MPMCTA). Its sensitivity to detect vascular lesions is even superior to conventional autopsy. The application of MPMCTA for cases of gunshot and sharp-trauma is therefore an obvious choice, as vascular lesions are common in such victims. In most cases of sharp trauma and in several cases of gunshots, death can be attributed to exsanguinations. MPMCTA is able to detect the exact source of bleeding and also to visualize trajectories, which are of most importance in these cases. The reconstructed images allow to clearly visualizing the trajectory in a way that is easily comprehensible for not medically trained legal professionals. The sensitivity of MPMCTA for soft tissue and organ lesions approximately matches the sensitivity of conventional autopsy. However, special care, experience and effective use of the imaging software is necessary for performing the reconstructions of the trajectory. Large volume consuming haemorrhages and shift of inner organs are sources of errors and misinterpretations. This presentation shall give an overview about the advantages and limitations of the use of MPMCTA for investigating cases of gunshot and sharp-trauma.

Plaies douloureuses: un défi quotidien, non une fatalité [Painful wounds : a daily challenge, not a fatality]

Long neglected, the pain related to wounds is nowadays recognized as an important issue. This article reviews the physiopathological mechanisms and the types of pain related to wounds, their assessment modalities as well as the pharmacological and non-pharmacological analgesic treatments.

Protocole pour l'évaluation et la prise en charge des plaies chroniques [Protocol for the evaluation and treatment of chronic wounds in the home care setting]

In 2001, it became evident that the domiciliary care nurses needed a tool to assist them in treating patients with chronic wounds. A protocol was therefore developed which could be used not only by the nurses but also by doctors and other health care professionals working in home care. As a parallel measure, a network of nurses specialised in wound care and available for advice and consultation was established.

An extraordinary case of an intracranial foreign body after a gunshot to the head.

Intermediate targets (IT) can modify the morphology of an entrance wound, the trajectory of the bullet, and contaminate the path with fragments or material from the target. The penetration into the body of big fragments or even of an entire IT is exceptional and only rarely reported in the literature. The interpretation of a gunshot wound after contact of the bullet with IT can sometimes be very tricky as the classical morphology can be missing. The presented case is a rare example of atypical entrance wound and path due to a surprising intermediate target of a gunshot fired against the head.

A large bullet in the bladder.

All manner of foreign bodies have been extracted from the bladder. Introduction into the bladder may be through self-insertion, iatrogenic means or migration from adjacent organs. Extraction should be tailored according to the nature of the foreign body and should minimise bladder and urethral trauma. We report a case of a bullet injury to the bladder, which finally presented as a gross hematuria after remaining asymptomatic for four years. We present here an alternative to suprapubic cystostomy with a large bladder foreign body treated via a combined transurethral unroofing followed by removal using a grasper passed through a suprapubic laparoscopic port.

Probabilistic evidential assessment of gunshot residue particle evidence (Part I): likelihood ratio calculation and case pre-assessment using Bayesian networks

Well developed experimental procedures currently exist for retrieving and analyzing particle evidence from hands of individuals suspected of being associated with the discharge of a firearm. Although analytical approaches (e.g. automated Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDS) microanalysis) allow the determination of the presence of elements typically found in gunshot residue (GSR) particles, such analyses provide no information about a given particle's actual source. Possible origins for which scientists may need to account for are a primary exposure to the discharge of a firearm or a secondary transfer due to a contaminated environment. In order to approach such sources of uncertainty in the context of evidential assessment, this paper studies the construction and practical implementation of graphical probability models (i.e. Bayesian networks). These can assist forensic scientists in making the issue tractable within a probabilistic perspective. The proposed models focus on likelihood ratio calculations at various levels of detail as well as case pre-assessment.

Stab wounds in a Swiss emergency department: a series of 80 consecutive cases.

Background: Interpersonal violence is a worldwide social reality which seems to increasingly affect even the safest of countries, such as Switzerland. In this country, road traffic accidents, as well as professional and recreational activities, are the main providers of trauma-related injuries. The incidence of penetrative trauma related to stab wounds seems to be regularly increasing in our ED. The question arises of whether our strategies in trauma management are adapted to deal efficiently with these injuries.Methods: To answer this question, the study analysed patients admitted for intentional penetrative injuries in a tertiary urban emergency department (ED) during a 23 month period. Demographics, conditions of the assault, injury type and treatments applied were analysed.Results: Eighty patients admitted due to an intentional penetrating trauma accounted for 0.2% of the surgical practice of our ED. The assault occurred equally in a public or a private context, mainly affecting young males during the night and the weekend. Sixty six patients (83%) were treated as out-patients. Only 10 patients needed surgery. None of them required damage control surgery. No patient died and the mean hospital stay was 5.5 days.Conclusions: The prevalence of stab wounds in Switzerland is low. These injuries rarely need complex, surgical procedures. Observational strategies should be considered according to the patient status.