Activity level DNA evidence evaluation: on propositions addressing the actor or the activity

More often than not, the source of DNA traces found at a crime scene is not disputed, but the activity or timing of events that resulted in their transfer is. As a consequence, practitioners are increasingly asked to assign a value to DNA evidence given propositions about activities provided by prosecution and defense counsel. Given that the dispute concerns the nature of the activity that took place or the identity of the actor that carried out the activity, several factors will determine how to formulate the propositions. Determining factors are (1) whether defense claims the crime never took place, (2) whether defense claims someone other than the accused (either an unknown individual or a known person) performed the criminal activity, and (3) whether it is claimed and disputed that the suspect performed an alternative, legitimate activity or has a relation to the victim, the object, or the scene of crime that implies a legitimate interaction. Addressing such propositions using Bayesian networks, we demonstrate the effects of the various proposition sets on the evaluation of the evidence.Criminal Justice: Legitimacy, accountability, and effectivit

Combining forensic evidence

In this thesis I consider the evaluation of a combination of different pieces of evidence in a legal and a forensic context. Evaluation of forensic evidence is the main topic of a research area called forensic statistics. In forensic statistics, the likelihood ratio framework is regarded as the standard for evaluating evidence. In legal practice, it is common that two competing propositions are presented to the trier of fact. The trier of fact needs to establish whether the proposition presented by the prosecution can be proven to the extent that there could be no ‘reasonable doubt’ in the mind of a ‘reasonable person’ that the defendant is guilty. The presented evidence should rule out any reasonable doubt. The likelihood ratio framework is based on probabilistic inference by applying Bayes’ Theorem. It allows for the transition from prior (initial) belief regarding the presented propositions to posterior (final) beliefs. This transition is based on the conditional probabilities to observe the evidence given the propositions (the likelihood ratio). In forensic casework, it is common that multiple pieces of evidence that need to be evaluated in terms of their support regarding the presented propositions are available. The most straightforward way of doing this for a forensic expert is by presenting a separate likelihood ratio for each individual piece of evidence. However, when doing so, one needs to be confident that the individual reports are optimally combined by the trier of fact. When forensic experts believe that their knowledge regarding the dependency structure between pieces of evidence is lost by presenting the likelihood ratios separately, one should strive to combine this evidence before it is sent to the trier of fact. Especially in situations where the pieces of evidence are of the same type (e.g. two shoe marks), one usually cannot regard them as conditionally independent observations and a combined evaluation is needed to prevent unnecessary misconceptions

A Coin tossing strategy for a High-Low guessing game

Consider the following guessing game: Lucy thinks of a number that is in between 0 and 100 and James tries to guess it as fast as possible. Lucy says ’Higher’ when the guess is too low and she says ’Lower’ when the guess is too high. A good strategy for James is tossing 100 fair coins where the first guess is equal to the number of coins that show heads. If this guess is too low he retosses all the tail coins and if the guess is too high he retosses all the head coins. What is the expected number of tosses in this strategy? This leads to all kinds of coin tossing problems. Most notably a problem by Råde. I discuss this problem and I consider how James may improve his strategy by adapting the coins. This leads to recursive problems.MathematicsElectrical Engineering, Mathematics and Computer Scienc

Combined evidential value of forensic DNA profiles

In forensic science it is common practice to work on problems where the likelihood ratio is based on observing single piece of evidence given two hypotheses. However, in a lot of cases, there is more than one piece of evidence. In this thesis three problems regarding combining DNA profiles are discussed. First, we derived a method to combine the evidential value of different partial Y-chromosomal DNA profiles of different stains. The method consists of finding a lower bound for the likelihood ratio when more than two propositions are compared and where we don't need the prior probabilities of the different propositions. Second, we made a simulation model to investigate the dendence of autosomal and Y chromosomal DNA profiles by assuming that everybody with the same Y-chromosomal DNA profile has a common ancestor and simulating the assignment of autosomal DNA profiles over different family tree structures. The results can be used in practice as scientific support for the assumption of independence between the Y and autosomal profile. Third, we developed a model to interpret (low-template) DNA profiles which is able to give the likelihood of observing the DNA profile given any allele-combination of the donor. This model assumes that a DNA profile is a result of a stochastic process where the input are the alleles of a possible donor. This model uses the information in peak heights without using any threshold. The model shows promising results in determining the combined evidential value of several low template DNA profiles that were obtained from the same stain.StatisticsElectrical Engineering, Mathematics and Computer Scienc

Portret van twee negentiende-eeuwse meesters: Leven en werk van Hendrik Jan en Cornelis Hendrik van Ameron

Leven en werk van de kunstschilder Hendrik Jan (1776-1833) en diens zoon Cornelis Hendrik van Amerom (1804-1874) zijn nauw verbonden met het kunstonderwijs in Arnhem en Leiden. De vroegste geschiedenis van de Arnhemse Kunstakademie is niet te denken zonder de invloed van Hendrikjan van Amerom. Als "eerste tekenmeester" bepaalde hij dertig jaar lang het onderwijs aan deze instelling. Zijn zoon, Cornelis Hendrik, speelde een belangrijke rol in het tekenonderricht te Leiden, waar hij les gaf aan diverse kostscholen voor jongens en meisjes uit de "betere standen". Cornelis Hendrik van Amerom kan tot de vroegste fotografen in Nederland worden gerekend. Tevens mag hij worden beschouwd als ontdekker van het Gelderse landschap, dat inspiratiebron werd voor vele kunstenaars. Hiermee is hij een directe voorloper van de schilders van de "Oosterbeekse Schildersbent" en de "Haagse School". Van uitzonderlijke (kunst)historische betekenis is zijn "Memorie-boekje". In dit tot nu toe onopgemerkt gebleven ego-document maakte hij belangrijke aantekeningen over zijn familie en zijn werk als kunstenaar en fotograaf. Het "Memorie-boekje" wordt in deze uitgave, met een geïllustreerde oeuvrecatalogus van beide kunstenaars, integraal gepubliceerd. Uitgave van Stichting Leids Kunsthistorisch Jaarboek