Handwriting evidence evaluation based on the shape of characters: application of multivariate likelihood ratios

A novel Bayesian methodology has been developed to quantitatively assess handwriting evidence by means of a likelihood ratio (LR) designed for multivariate data. This methodology is presented and its applicability is shown through a simulated case of a threatening anonymous text where a suspect is apprehended. The shape of handwritten characters a, d, o, and q of the threatening text was compared with characters of the true writer, and then with two other writers, one with similar and one with dissimilar characters shape compared to the true writer. In each of these three situations, 100 draws of characters were made and the resulting distributions of LR were established to consider the natural handwriting variation. LR values supported the correct hypothesis in every case. This original Bayesian methodology provides a coherent and rigorous tool for the assessment of handwriting evidence, contributing undoubtedly to integrate the field of handwriting examination into science.     

Death by potassium chloride intravenous injection: evaluation of analytical detectability

Potassium chloride intravenous injection is used in suicide attempts and lethal procedures for state-sanctioned punishment. Owing to its relatively high concentrations in hemolyzed blood (25-80 mM) compared to serum (about 4 mM), it is difficult to conclude potassium poisoning by postmortem analysis of biologic samples. A 41-year-man was found dead with an injection sign on his foot and a syringe close to the corpse. No particular signs were noted during the autopsy. Blood, bile, and urine were submitted to xenobiotic screening procedures used in the laboratory. Syringe content was found positive to potassium ions. Blood potassium concentration was determined by ion-selective electrode measurement (range 3.0-150 mM). Blood was found positive for diazepam at therapeutic level. Potassium concentration was 160.0 (cardiac) and 87.3 mM (femoral blood). Our results show that potassium concentration was significantly higher in heart blood in a suicide case. Hence, the general issue of considering potassium poisoning hardly demonstrable by toxicology needs to be questioned and thoroughly studied.     

Determination of stature from skeletal and skull measurements by CT scan evaluation

The aim of this article is to find a correlation between height and femur/skull measurements through Computed Tomography (CT) scans and derive regression equations for total skeletal height estimation in the Caucasian population. We selected 200 Caucasian patients from March 2010 to July 2011 who had to perform a CT scan for cancer restaging. The mean age is 64.5 years. Both sexes are represented by the same number of persons. Patients have executed a total body CT scan with contrast; once scan accomplished, we measured height through a digital scales. We analyzed CT scans of each patient, obtaining multiplanar reconstruction in sagittal and coronal planes with 1mm of thickness, and we measured 10 diameters of skull and femur. Then we performed a single and a multiple regression analysis considering the three diameters that better correlated with height. The skeletal diameters with the highest correlation coefficients with stature were femur lengths, length of cranial base (Ba-N), and distance from the posterior extremity of the cranial base to the inferior point of the nasal bone (Ba-NB). Although both femur and skull are skeletal segments used for stature estimation, in our sample femur gave stronger correlation with height than skull. h=35.7+1.48·BaN+2.32·BaNB+2.53·FEM and h=3.06·FEM+72.6 are the formulae that provided the most accurate stature assessment using multiple and single regression analysis respectively.     

The database search problem: A question of rational decision making

This paper applies probability and decision theory in the graphical interface of an influence diagram to study the formal requirements of rationality which justify the individualization of a person found through a database search. The decision-theoretic part of the analysis studies the parameters that a rational decision maker would use to individualize the selected person. The modeling part (in the form of an influence diagram) clarifies the relationships between this decision and the ingredients that make up the database search problem, i.e., the results of the database search and the different pairs of propositions describing whether an individual is at the source of the crime stain. These analyses evaluate the desirability associated with the decision of 'individualizing' (and 'not individualizing'). They point out that this decision is a function of (i) the probability that the individual in question is, in fact, at the source of the crime stain (i.e., the state of nature), and (ii) the decision maker's preferences among the possible consequences of the decision (i.e., the decision maker's loss function). We discuss the relevance and argumentative implications of these insights with respect to recent comments in specialized literature, which suggest points of view that are opposed to the results of our study.     

Nanotechnology for forensic sciences: Analysis of PDMS replica of the case head of spent cartridges by optical microscopy, SEM and AFM for the ballistic identification of individual characteristic features of firearms

A novel application of replica molding to a forensic problem, viz. the accurate reproduction of the case head of gun and rifle cartridges, prior and after been shot, is presented. The fabrication of an arbitrary number of identical copies of the region hit by the firing pin and by the breech face is described. The replicas can be (i) handled without damaging the original evidence, (ii) distributed to different law enforcement agencies for comparison against other evidences found on crime scenes or ballistic tests of seized firearms, (iii) maintained on a file by the laboratories. A detailed analysis of the morphological features of the replicas has been carried out by standard microscopy techniques as well as by advanced microscopy such as scanning probe and scanning electron leading to a quantitative morphological characterization of the case heads down to the nanometer scale. The assignment of the cartridge replicas to the shooting weapon is demonstrated to hold below the micron scale, while it is hindered at the nanometer level both by the manufacturing differences and by eventual modifications occurring on the firing pin.     

Uncertainty about the true source. A note on the likelihood ratio at the activity level

This paper focuses on likelihood ratio based evaluations of fibre evidence in cases in which there is uncertainty about whether or not the reference item available for analysis - that is, an item typically taken from the suspect or seized at his home - is the item actually worn at the time of the offence. A likelihood ratio approach is proposed that, for situations in which certain categorical assumptions can be made about additionally introduced parameters, converges to formula described in existing literature. The properties of the proposed likelihood ratio approach are analysed through sensitivity analyses and discussed with respect to possible argumentative implications that arise in practice.     

Applicability of Greulich and Pyle and Demirijan aging methods to a sample of Italian population

Age estimation in forensics is essential in cases involving both living and dead subjects. For living subjects, age estimation may be used to establish an individual's status as a minor in cases involving adoption, criminal responsibility, child pornography, and those seeking asylum. Criteria for age estimation in the living have recently been put forth by The Study Group on Forensic Age Diagnostics. The group has proposed guidelines with a three-step procedure: a physical examination and anthropometrical analysis; dental analysis by orthopantomogram (OPG); and X-ray study of the left hand and wrist. The board of FASE highlighted advantages and limits of each method, and suggested practical solutions concerning the age estimation process for adults and subadults. The aim of this study was to verify the applicability of the Greulich and Pyle, and Demirjian techniques on a sample group of Italians, whose ages were known, in determining the skeletal and dental age, in addition to evaluating the reliability of these techniques. 535 subjects between the ages of 7 and 15years were examined, each one undergoing both an orthopantomography (OPG) and radiography of the left wrist and hand. The data obtained underwent statistical analysis. The analyses have shown that a correlation exists between skeletal and dental age, and real age. Age estimation carried out using the Greulich and Pyle method has shown itself to be especially accurate on the Italian sample, particularly in the age ranges of 7-9years and 10.4-11.5years. The Greulich and Pyle method has shown itself to be reliable for the sample analyzed notwithstanding the ethnic differences between the original sample of reference and those analyzed in this study. Application of the Demirjian technique resulted in an overestimation of dental age. This difference is shown to be more highly significant in the higher age ranges. The combination of the Greulich and Pyle, and Demirjian methods have revealed a difference regarding real age, which turns out to be more modest in the younger age ranges and more significant in older subjects.     

Bayesian networks and the value of the evidence for the forensic two-trace transfer problem*

Forensic scientists face increasingly complex inference problems for evaluating likelihood ratios (LRs) for an appropriate pair of propositions. Up to now, scientists and statisticians have derived LR formulae using an algebraic approach. However, this approach reaches its limits when addressing cases with an increasing number of variables and dependence relationships between these variables. In this study, we suggest using a graphical approach, based on the construction of Bayesian networks (BNs). We first construct a BN that captures the problem, and then deduce the expression for calculating the LR from this model to compare it with existing LR formulae. We illustrate this idea by applying it to the evaluation of an activity level LR in the context of the two-trace transfer problem. Our approach allows us to relax assumptions made in previous LR developments, produce a new LR formula for the two-trace transfer problem and generalize this scenario to n traces.     

Unusual sources of Sn in GSR. An experimental study by SEM and IBA

Gunshot Residue (GSR) produced by the discharge of a firearm often provides very useful information in criminal investigations in cases involving the use of firearms. Scanning Electron Microscopy equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDS) is typically used worldwide to visualize micrometric particles constituting GSR and to analyse their elemental composition. The 2017 ASTM Standard guide for gunshot residue analysis by scanning electron microscopy/energy dispersive X-ray spectroscopy specifies that “Particles classified as characteristic of GSR will have one of the following elemental compositions: Lead, antimony, barium; Lead, barium, calcium, silicon, tin”. For the first time, the presence of an additional element, such as Sn, plays a key role in ASTM particle classification. It is known that some ammunitions, used for pistols, revolvers and rifles, contain tin foil discs for sealing the primer mixture into the cup, resulting in GSR particles containing Sn. The authors faced some cases in which Sn was unexpectedly found in GSR particles from a 0.22 Long Rifle derringer and from some 12 gauge shotguns. No tin foil discs are used in rimfire ammunitions and there is no published evidence of tin foil discs in shotshell ammunitions. Following a “case by case” approach, experimental research has been carried out to explain how Sn can be present in GSR particles when the last discharged cartridge also does not contain any Sn either in components and in the explosive charges.Moreover, the use of Particle Induced X-ray Emission (PIXE) showed the capability to overcome overlap ambiguity of Sb and Sn peaks in the X-ray spectra, being a possible key issue in real shooting cases if Sn quantities are below the lower limit of SEM detection, especially when Sb is also present.     

Litigation,Judicial Path-Dependence,and Legal Change

In this paper we consider the role that litigation and case selection play in the process of legal change. After identifying two necessary conditions for litigation, we examine the effect of judicial path dependence on the consolidation of liability rules and legal remedies, paying special attention to litigation with different win–loss ratios. We study the consequence of private litigation decisions on the contraction or consolidation of legal rules under various litigation and judicial environments. We also consider the relevance of the win–loss ratios, the existence and nature of positive litigation costs, and the weight of past precedents on the ongoing process of legal evolution.JEL K0, K40, K13, K41