Netherlands Forensic Institute Research Articles

From data to a validated score-based LR system: A practitioner’s guide

Likelihood ratios (LRs) are a useful measure of evidential strength. In forensic casework consisting of a flow of cases with essentially the same question and the same analysis method, it is feasible to construct an ‘LR system’, that is, an automated procedure that has the observations as input and an LR as output. This paper is aimed at practitioners interested in building their own LR systems. It gives an overview of the different steps needed to get to a validated LR system from data. The paper is accompanied by a notebook that illustrates each step with an example using glass data. The notebook introduces open-source software in Python constructed by NFI (Netherlands Forensic Institute) data scientists and statisticians.

Postmortem redistribution of amphetamines and benzodiazepines in humans: Important variables that might be influencing the central blood / peripheral blood ratio

IntroductionThe primary objective of postmortem forensic toxicology is to determine if toxicological substances detected in bodily material of victims have contributed to the death of the victim. Interpretation of postmortem drug concentrations is hindered by the fact that time and site dependent variations in postmortem drug concentrations occur, as a result of postmortem redistribution (PMR). An often-used marker for the occurrence of PMR, is the cardiac blood concentration/peripheral blood concentration ratio (C/P ratio) of a drug. In this study, we investigated the relationship between 13 variables and the C/P ratios of amphetamines and benzodiazepines. MethodToxicological results of all postmortem cases that were positive for amphetamines (amphetamine, MDMA, MDA) and/or benzodiazepines (diazepam, desmethyldiazepam, temazepam, oxazepam, midazolam, α-hydroxymidazolam) investigated by the Netherlands Forensic Institute between January 1 2010 and July 31 2020 were reviewed. A total of 112 amphetamine positive cases (224 paired specimen) and 179 benzodiazepine positive cases (358 paired specimen) were selected. The C/P ratios were determined for all selected cases. Ratios were compared between subgroups by performing either a Mann-Whitney U test or a Kruskal-Wallis test followed by post-hoc Mann-Whitney U test. ResultsAfter dividing cases in quartiles based on their amphetamine concentration in femoral blood, the amphetamine C/P ratio was significantly lower in cases with a high amphetamine concentration (quartile 4) compared to cases with a low amphetamine concentration (quartiles 1 and 2) with median C/P ratios of 1.6, 2.4 and 2.2, respectively (p-value<0.001 and p-value=0.001, respectively).The MDA C/P ratio was significantly higher in cases where trauma was the cause of death compared to cases where intoxication was the cause of death with median C/P ratios of 3.3 and 1.6, respectively (p-value<0.001). The MDA C/P ratio was also significantly lower in cases where resuscitation was attempted compared to cases where no resuscitation was attempted with median C/P ratios of 1.6 and 2.4, respectively (p-value=0.003). However, a significant dependency between the variables cause of death and attempted resuscitation was observed.No significant differences in benzodiazepine C/P ratios were observed between subgroups of any of the investigated variables. However, the low p-value of BMI suggests a potential difference in midazolam C/P ratio between BMI subgroups (p-value=0.027). ConclusionWhen interpreting postmortem toxicological results, it might prove useful to take the above-mentioned variables into account.

Bloodstain pattern analysis & Bayes: A case report

The findings from a bloodstain pattern analysis (BPA) may assist in formulating or falsifying scenarios that are considered in the investigative stages of a criminal investigation. When a case proceeds to trial the bloodstain pattern expert may be asked about the relevance of their findings given scenarios that are proposed by the prosecution and defense counsel. Such opinions provided by an expert are highly relevant to police investigation or legal proceedings, but the reasoning behind the opinion or implicit assumptions made by the expert may not be transparent.A proper framework for the evaluation of forensic findings has been developed since the late twentieth century, based on the hierarchy of propositions, Bayesian reasoning and a model for case assessment and interpretation. This framework, when implemented in casework, mitigates some of the risks of cognitive biases, and makes the reasoning and scientific basis for the opinion transparent. This framework is broadly used across forensic science disciplines. In this paper we describe its application to the field of BPA using a case example from the Netherlands Forensic Institute (NFI).

A fatal mono-intoxication with 4-fluoroisobutyrylfentanyl: Case report with postmortem concentrations.

We report on a case of a 35-year-old man who died suddenly and unexpectedly due to a 4-fluoroisobutyrylfentanyl (4-FIBF) mono-intoxication. Pathological, toxicological and chemical investigations were conducted at the Netherlands Forensic Institute. A full three-cavity forensic pathological examination was performed according to international guidelines. Biological samples obtained during autopsy were comprehensively investigated for the presence of toxic substances using headspace gas chromatography (GC) with flame ionization detection, liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS), GC-MS, high-performance LC with diode array detection and LC-tandem MS (LC-MS-MS). The seized crystalline substance found next to the body was investigated using a presumptive color test, GC-MS, Fourier-transform infrared spectroscopy and nuclear magnetic resonance. Pathological investigation identified minor lymphocytic infiltrates in the heart, considered irrelevant for the cause of death. Toxicological analysis of the victims' blood indicated the presence of a fluorobutyrylfentanyl (FBF) isomer, with no other compounds detected. The FBF isomer was identified in the seized crystalline substance as 4-FIBF. 4-FIBF concentrations were quantified in femoral blood (0.030 mg/L), heart blood (0.12 mg/L), vitreous humor (0.067 mg/L), brain tissue (>0.081 mg/kg), liver tissue (0.44 mg/kg) and urine (approximately 0.01 mg/L). Based on the outcomes of the pathological, toxicological and chemical investigations, the cause of death of the deceased was attributed to a fatal 4-FIBF mono-intoxication. The presented case underlines the added value of a combined bioanalytical and chemical investigative approach to identify and subsequently quantify fentanyl isomers in postmortem cases. Furthermore, it demonstrates the importance of investigating the postmortem redistribution of novel fentanyl analogs to establish reference values and to subsequently allow for correct interpretation of cause of death analysis in future casework.

The influence of storage conditions on fingermarks developed with 1,2-indanedione-ZnCl

The most important class of reagents for the enhancement of fingermarks on porous surfaces are those that react with the amino acid constituents of fingermarks. Ninhydrin, DFO (1,8-diazafluoren-9-one), and 1,2-indanedione are the three most common techniques widely known in forensic laboratories for the visualization of latent fingermarks on porous surfaces. In 2012 the Netherlands Forensic Institute replaced DFO by 1,2-indanedione-ZnCl after an internal validation, just like an increasing numbers of laboratories. In 2003, Gardner et al. published an article showing that fingermarks treated with 1,2-indanedione (without ZnCl), that were stored in daylight only decreased by 20% in fluorescence in 28 days. However, during casework we observed that the fluorescence of fingermarks treated with 1,2-indanedione with ZnCl decreased more rapidly. In this study, the effect of various storage conditions and aging times on the fluorescence of marks after treatment with 1,2-indanedione-ZnCl were assessed. Latent printed fingermarks from the digital matrix printer (DMP) and natural fingermarks from a known donor were used. The results showed that storing fingermarks in daylight (wrapped and un-wrapped) drastically decrease (over 60% loss) in fluorescence in approximately three weeks. Storage of the marks in a dark environment (at room temperature, in the refrigerator or even in the freezer) resulted in a decrease in fluorescence of less than 40%. Our recommendation is to always store treated fingermarks with 1,2-indanedione-ZnCl in a dark environment and, if possible, photographing them directly (within 1–2 days after treatment) to minimize the decrease of fluorescence.

Postmortem redistribution of cocaine and its metabolites, benzoylecgonine and ecgonine methyl ester in humans: Important variables that might be influencing the central blood / peripheral blood ratio

IntroductionA big challenge in forensic toxicology is the correct interpretation of the results of quantitative analyses in postmortem cases. Postmortem drug concentrations not necessarily reflect the drug concentrations at the time of death, due to postmortem changes in drug concentrations caused by postmortem redistribution (PMR). Cardiac blood is more prone to PMR related concentration changes than peripheral blood. Because of this difference in susceptibility to PMR related concentration changes, the ratio of cardiac blood concentration/peripheral blood concentration (C/P) of a drug is an often-used marker of PMR. In this study, we investigated the relationship between different potentially significant variables and the C/P ratios of cocaine, benzoylecgonine (BE) and ecgonine methyl ester (EME) in humans. The aim was to elucidate the mechanisms involved in PMR of these substances and potentially provide guidelines aiding forensic toxicologists in the interpretation of postmortem quantitative results of cocaine and its metabolites. To differentiate between postmortem concentration changes due to redistribution versus degradation of cocaine, the relationships between these variables and metabolite/cocaine ratios were investigated as well. MethodToxicological results of all postmortem cases that were positive for cocaine, BE and/or EME investigated by the Netherlands Forensic Institute between January 1st 2010 and July 31st 2020 were reviewed. The C/P ratios, BE/cocaine ratios and EME/cocaine ratios were determined for all selected cases. Cocaine, BE and/or EME were quantified in both femoral blood and cardiac blood in a total of 148 cases. Ratios were compared between subgroups by performing either a Mann-Whitney U test or a Kruskal-Wallis test followed by post-hoc Mann-Whitney U test. ResultsA statistically significant difference in C/P ratio of EME was observed between trauma and non-trauma cases with median C/P ratios of 2.03 and 1.57, respectively (p value=0.001). A statistically significant difference in EME/cocaine ratio was observed between the BMI subgroups 18.5 – 25.0 kg/m2 and> 25 kg/m2 with median EME/cocaine ratios of 3.79 and 1.58, respectively (p-value<0.001). ConclusionPostmortem cocaine concentrations should be interpreted with caution, considering the occurrence of both PMR and postmortem degradation. When interpreting postmortem toxicological results in cocaine-related fatalities, it might prove useful to take the above-mentioned variables into account.

Generalized fiducial factor: An alternative to the Bayes factor for forensic identification of source problems

One formulation of forensic identification of source problems is to determine the source of trace evidence, for instance, glass fragments found on a suspect for a crime. The current state of the science is to compute a Bayes factor comparing the marginal distribution of measurements of trace evidence under two competing propositions for whether or not the unknown source evidence originated from a specific source. The obvious problem with such an approach is the ability to tailor the prior distributions (placed on the features/parameters of the statistical model for the measurements of trace evidence) in favor of the defense or prosecution which is further complicated by the fact that the typical number of measurements of trace evidence is typically sufficiently small that prior choice/specification has a strong influence on the value of the Bayes factor. To remedy this problem of prior specification and choice, we develop an alternative to the Bayes factor, within the framework of generalized fiducial inference, that we term a generalized fiducial factor. Furthermore, we demonstrate empirically, on synthetic and real Netherlands Forensic Institute casework data, deficiencies in Bayes factor and classical/frequentist likelihood ratio approaches.

Reporting on forensic biology findings given activity level issues in the Netherlands

There appears to be some hesitation within the forensic biology community to formally evaluate and report on findings given activity level propositions. This hesitance in part stems from concerns about the lack of relevant data on the dynamics of biological traces and doubt about the relevance of such expert opinions to the trier of fact. At the Netherlands Forensic Institute formal evaluative opinions on the probability of case findings given propositions at the activity level are provided since 2013, if requested by a mandating authority. In this study we share the results from a retrospective analysis of 74 of such requests. We explore which party initiates requests, the types of cases that are submitted, the sources of data being used to assign probabilities to DNA transfer, persistence, prevalence and recovery (TPPR) events, the conclusions that were drawn by the scientists, and how the conclusions were used by the courts. This retrospective analysis of cases demonstrates that published sources of data are generally available and can be used to address DNA TPPR events in most cases, although significant gaps still remain. The study furthermore shows that reporting on forensic biology findings given activity level propositions has been generally accepted by the district and appeal courts, as well as the other parties in the criminal justice system in the Netherlands.

Automated DNA casework workflow: A retrospective study of the first implementation of FIDL at the Netherlands Forensic Institute

FIDL is a fast and automated DNA identification line which represents a series of software solutions automating the process from raw capillary electrophoresis data to reporting. This retrospective study provides insight in the numbers of cases, turnaround time, results compared to the standard workflow and the benefits automation has in a large volume workflow.

Addition of an adipose marker to the organ tissue identification mRNA assay

At the Netherlands Forensic Institute, mRNA profiling for the purpose of organ tissue identification is frequently requested in casework. The previous version of the assay (denoted Organtyper) lacked markers for identifying adipose tissue, while this was occasionally questioned in casework. Here, three potential adipose markers are examined before incorporating one into the final Organtyper assay. The added value of the adipose marker becomes clear from looking at casework results.

Postmortem redistribution of morphine in humans: Important variables that might be influencing the central blood/peripheral blood ratio

IntroductionIn the field of forensic toxicology, many unexpected deaths are investigated as to whether toxicological substances may have caused or contributed to someone’s death. One of the factors that makes interpretation of the results of quantitative analysis in postmortem toxicology challenging, is that measured postmortem drugs levels may vary according to the sampling site and the interval between death and specimen collection. These site- and time-dependent variations are caused by ‘postmortem redistribution’ (PMR). Literature shows that there are several factors that determine the degree of PMR, such as cell and tissue changes after death, decomposition and the physicochemical characteristics of drugs. Blood from peripheral sites seems to be less affected by PMR than cardiac blood. Therefore, the ratio of cardiac blood concentration/peripheral blood concentration (C/P) of a drug is often used as a marker of the extent of postmortem redistribution. In this study, we investigated the relationship between different potentially important variables and the C/P ratio of morphine in humans in order to provide new insights that might assist in the interpretation of quantitative results in forensic casework. MethodToxicological results of all morphine positive postmortem cases investigated by the Netherlands Forensic Institute between January 1, 2010 and July 31, 2020 were reviewed. Morphine was quantified in both femoral and cardiac blood in a total of 103 cases. The C/P ratios were determined for all selected cases. To collect data for this study, all corresponding files were reviewed. C/P ratios were compared between subgroups by performing either a Mann-Whitney U test or a Kruskal-Wallis test, followed by a post-hoc Mann-Whitney U test. Bonferroni correction was performed to correct for the likelihood of a significant result by chance due to multiple testing. After Bonferroni correction, a p-value< 0.004 was considered statistically significant. ResultsThe data suggests a relationship between grade of decomposition at autopsy, position of the corpse at discovery, route of administration, attempted resuscitation and the C/P ratio of morphine with p-values of 0.010, 0.026, 0.035 and 0.046, respectively. ConclusionGrade of decomposition at autopsy, position of the corpse at discovery, route of administration and attempted resuscitation seem to be influencing the C/P ratio of morphine. Of these four variables, the route of administration seems to have the greatest impact.

De rechten van de verdediging in de context van omvangrijke datasets en geavanceerde zoekmachines in strafzaken: een suggestie voor uitbreiding

Criminal cases increasingly revolve around extensive datasets consisting of digital evidence and advanced technological search tools such as Hansken, a big data forensic tool developed by the Netherlands Forensic Institute. In this context, lawyers and scientists have already argued that advanced search tools significantly strengthen the position of the prosecution at the expense of the defense, which generally does not have access to these tools. As a result, the defense has little influence to help determine what counts as relevant information in a criminal case and has hardly any possibilities to find exculpatory evidence and to test the reliability of digital evidence. This in turn leads to significant power and knowledge asymmetry. The principle of equality of arms as a core part of the right to a fair trial in Article 6 of the European Convention on Human Rights provides a good basis for the development of new or more extensively interpreted defence rights that are needed in the digital age. Based on an analysis of recent ECtHR case law, I discuss the level of established rights of the defense with regard to access to the dataset(s) and the advanced search tool in criminal proceedings. Thinking further as to the possible and desirable procedural guarantees in this novel context, I then discuss how the reliability of digital evidence and the process though which it was produced can be ensured and tested by the defence through a logging obligation and a right to counter-expertise.

Visual Analysis of the External Characteristics and Research Hotspots of Literatures in International Forensic Science.

Objective To analyze the forensic science-related literature included in the Web of Science database in the recent decade through bibliometric methods, to provide reference for relevant research. Methods Literatures were searched in 3 ways： Subject search, Journal search and Institution search. The annual distribution, national （regional） distribution, institution distribution, journal distribution and the research hotspots of the related literatures were analyzed through Thomson Data Analyzer （TDA）, Ucinet, VOSviewer, and so on. Results A total of 49 469 related literatures were included in the recent decade. The number of literatures continued to climb year by year. The top 15 countries （regions） accounted for 78.52% of the total number of published literatures, and China ranked 5th, but ranked 12th in terms of the proportion of high-cited papers; Netherlands, Switzerland, Australia, etc. had high comprehensive influence. The number of countries （regions） that cooperated with China were 129, including the United States, the United Kingdom and Germany. The Institute of Forensic Science of Saint Mary's University, University of Sydney and Netherlands Forensic Institute had high comprehensive influence, and the related literatures were published on 6 357 journals. According to high-frequency co-occurrence network and high-cited papers, brain injury, health policy, assessment scales and models and medical imaging were selected as research hotspots. Conclusion The total number of literatures in forensic science included in international SCI increased significantly, and the influence of China's achievements needs to be greatly enhanced; the research institutions were scattered, and China's research power needs to be continuously condensed; the research hotspots in international fields are extensive, and the international participation of China in top level research needs to be strengthened.

Defence Rights in the Context of Huge Data Sets and Big Data Forensic Tools in Criminal Proceedings

Criminal cases increasingly revolve around extensive data sets consisting of digital evidence and advanced technological search tools such as Hansken, a big data forensic tool developed by the Netherlands Forensic Institute. In this context, lawyers and scientists have already argued that advanced search tools significantly strengthen the position of the prosecution at the expense of the defence, which generally does not have access to these tools. As a result, the defence has little influence to help determine what counts as relevant information in a criminal case and has hardly any possibilities to find exculpatory evidence and to test the reliability of digital evidence. This in turn leads to significant power and knowledge asymmetry. The principle of equality of arms as a core part of the right to a fair trial in Article 6 of the European Convention on Human Rights provides a good basis for the development of new or more extensively interpreted defence rights that are needed in the digital age. Based on an analysis of recent ECtHR case law, I discuss the level of established rights of the defence with regard to access to the dataset(s) and the advanced search tool in criminal proceedings. Thinking further as to the possible and desirable procedural guarantees in this novel context, I then discuss how the reliability of digital evidence and the process though which it was produced can be ensured and tested by the defence through a logging obligation and a right to counter-expertise.

Evaluation of glass evidence at activity level: A new distribution for the background population

For evidence evaluation of the physicochemical properties of glass at activity level a well-known formula introduced by Evett & Buckleton [1,2] is commonly used. Parameters in this formula are, amongst others, the probability in a background population to find on somebody’s clothing the observed number of glass sources and the probability in a background population to find on somebody’s clothing a group of fragments with the same size as the observed matching group.Recently, for efficiency reasons, the Netherlands Forensic Institute changed its methodology to measure not all the glass fragments but a subset of glass fragments found on clothing. Due to the measurement of subsets, it is difficult to get accurate estimates for these parameters in this formula.We offer a solution to this problem. The heart of the solution consists of relaxing the assumption of conditional independence of group sizes of background fragments, and modelling the probability of an allocation of background fragments into groups given a total number of background fragments by a two-parameter Chinese restaurant process (CRP) [3]. Under the assumption of random sampling of fragments to be measured from recovered fragments in the laboratory, parameter values for the Chinese restaurant process may be estimated from a relatively small dataset of glass in other relevant cases.We demonstrate this for a dataset of glass fragments collected from upper garments in casework, show model fit and provide a prototypical calculation of an LR at activity level accompanied with a parameter sensitivity analysis for reasonable ranges of the CRP parameter values.Considering that other laboratories may want to measure subsets as well, we believe this is an important alternative approach to the evaluation of numerical LRs for glass analyses at activity level.

New psychoactive substances (NPS) in the Netherlands: occurrence in forensic drug samples, consumer drug samples and poisons center exposures between 2013 and 2017

Although European-wide data on the new psychoactive substances (NPS) drug market are available, country-specific data are limited. We studied recent NPS trend data relative to all recreational drugs on the Dutch drug market. National observational study. The Netherlands. Three national indicators were used between 2013 and 2017: 1) forensic drug samples offered to the Netherlands Forensic Institute (NFI); 2) drug samples submitted by consumers to the Drugs Information and Monitoring System (DIMS); and 3) exposures in which the Dutch Poisons Information Center (DPIC) was consulted. Overall NPS incidence rate was the primary outcome. Numbers and specific categories of NPS were also studied. Changes in NPS incidence rates over time were analyzed using Poisson regression analyses (year effect expressed as Incidence Rate Ratios [IRR]). From 2013-2017, NPS were involved in 1,892 forensic samples, 6,316 consumer samples, and 481 poisons center exposures. In 2013, NPS incidence rates were 2.5%, 7%, and 4% versus 3%, 11% and 11% in 2017, respectively in the NFI, DIMS and DPIC samples/exposures. NPS incidence rates increased significantly in consumer samples between 2013-2016 (IRR=1.23; 95% CI [1.18,1.29]) and in poisons center exposures between 2013-2017 (IRR=1.19; 95% CI [1.06,1.35]), while the trend in forensic samples appeared more stable. Phenethylamines were the largest class and were detected in 58%, 80% and 63% of NFI, DIMS and DPIC samples/exposures, respectively. Detected phenethylamines mainly involved 4-fluoroamphetamine and 2C-x derivatives. The second largest class were cathinones, which were detected in 21%, 11% and 16% of NFI, DIMS and DPIC samples/exposures, respectively. Analysis of forensic drug samples, consumer drug samples and exposures reported to poison centers from 2013 to 2017 shows the constant presence of new psychoactive substances (NPS) on the Dutch drug market and its use by the Dutch population. The two largest classes present in the Netherlands were phenethylamines and cathinones.

Minimizing hand-to-glove DNA contamination

In this study, the Netherlands Forensic Institute’s (NFI) contamination prevention recommendations to prevent hand-to-outside-glove DNA transfer were assessed for effectiveness and subsequently optimized. The results of this study support the choice of using a 0.3% sodium hypochlorite solution or commercially available RNase AWAY as decontamination reagents to clean and subsequently dry the exterior of donned gloves prior to entering the lab and/or handling items of evidence.

Implementation of the Dutch expertise centre for child abuse: descriptive data from the first 4 years

ObjectiveCombined paediatric and forensic medical expertise to interpret physical findings is not available in Dutch healthcare facilities. The Dutch Expertise Centre for Child Abuse (DECCA) was founded in the conviction...

A part-declared blind testing program in firearms examination

In 2015 and 2016 the Central Unit of the Dutch National Police created and submitted 21 cartridge case comparison tests as real cases to the Netherlands Forensic Institute (NFI), under supervision of the University of Twente (UT). A total of 53 conclusions were drawn in these 21 tests. For 31 conclusions the underlying ground truth was “positive”, in the sense that it addressed a cluster of cartridge cases that was fired from the same firearm. For 22 conclusions the ground truth was “negative”, in the sense that the cartridge cases were fired from different firearms. In none of the conclusions, resulting from examinations under casework conditions, misleading evidence was reported. All conclusions supported the hypothesis reflecting the ground truth. This article discusses the design and results of the tests in more detail.

Process Improvement and the Efficient Frontier: Forecasting the Limits to Strategic Change across Crime Laboratory Areas of Investigation

Undertaking programs for process improvement, such as Lean Six Sigma, permit a laboratory to do more with their limited resources. The Netherlands Forensic Institute (NFI) embraced a Lean Six Sigma change process that led to dramatic increases in capacity, while simultaneously reducing turnaround time (TAT) to a fraction of their historical experience. As other laboratories adopt similar process improvement programs, will those laboratories also experience similar results with higher productivity across the laboratory and reduced turnaround time in every area of scientific investigation? We demonstrate that similar success may be expected with a laboratory's current caseload, but the degree of improvement is related to the size of the political jurisdiction, crime rates, and the resulting caseload; and the degree of inefficiencies at the start of the process improvement program. An understanding of the economic forces at play enables laboratory management to better forecast outcomes and plan for the eventualities. Using data from Project FORESIGHT 2015–2016, tables are provided that permit laboratories to match their caseload within each area of investigation to the forensic laboratory standard for efficiency at that caseload.