Forensic Science Techniques Research Articles

Beliefs about error rates and human judgment in forensic science

Forensic science techniques are often used in criminal trials to infer the identity of the perpetrator of crime and jurors often find this evidence very persuasive. Unfortunately, two of the leading causes of wrongful convictions are forensic science testing errors and false or misleading forensic testimony (Saks and Koehler, 2005). Therefore, it is important to understand jurors’ pre-existing beliefs about forensic science, as these beliefs may impact how they evaluate forensic evidence in the courtroom. In this study, we examine people’s perceptions of the likelihood of error and human judgment involved at each stage of the forensic science process (i.e., collection, storage, testing, analysis, reporting, and presenting). In addition, we examine people’s perceptions of the accuracy of — and human judgment involved in — 16 different forensic techniques. We find that, in contrast to what would be expected by the CSI effect literature, participants believed that the process of forensic science involved considerable human judgment and was relatively error-prone. In addition, participants had wide-ranging beliefs about the accuracy of various forensic techniques, ranging from 65.18% (document analysis) up to 89.95% (DNA). For some forensic techniques, estimates were lower than that found in experimental proficiency studies, suggesting that our participants are more skeptical of certain forensic evidence than they need to be.

Tongue replica for personal identification: A digital photographic study

The tongue is a vital internal organ well encased within the oral cavity and protected from the environment. The morphology and surface features are characteristics of every individual, and these traits can be used for forensic identification. Aims: To examine and classify variations in morphological characteristics of the tongue as observed on digital photographs and to assess the usefulness of tongue replica for personal identification in forensic science. Settings and Design: A study was conducted in the Department of Oral Medicine and Radiology, M.R. Ambedkar Dental College, Bangalore, for a period of 3 months. Materials and Methods: In total, 100 (50 male and 50 female) study participants with an age range of 21 − 40 years were included in the study. The tongue was subjected to visual examination following which digital photographs of the dorsal surface of the tongue were taken to evaluate different morphological characteristics of the tongue. Statistical Analysis Used: Chi-square test. Results: The predominant shape of the tongue in both males and females was U-shape, V-shaped tongue with a sharp tip was observed in more number of females compared to males. Scalloped borders were more common in females compared to men. Single fissures were more common in females, and multiple fissures were more common in males. Conclusions: Variations in morphology and surface features of the tongue may constitute distinctiveness, which can be adopted by dentists as a chairside technique on a regular basis. This could serve as a database and a guide for personal identification. The lingual photographic image can enhance personal identification along with other techniques in forensic science.

Pilot study of feature-based algorithm for breech face comparison

A novel feature-based method, which is scale invariant feature transform (SIFT) and RANdom SAmple Consensus (RANSAC) integration algorithm, is introduced to promote the automated identification of the breech face impression, the most common mark left on the cartridge used for firearm evidence. SIFT algorithm is employed to extract the local extrema from examined impression as keypoints representing its invariant features, and to build the feature descriptor for each keypoint based on its local gradients in neighborhood. RANSAC is used to improve the matching performance among these keypoints and feature descriptors. With hypothesize-and-verify methods, RANSAC is able to construct the best model fitting initial matching pairs of keypoints and to guarantee the robust comparison result. Validation tests using 40 cartridge cases fired from pistols with 10 consecutively manufactured slides yielded a clear separation result, which strongly supports the effectiveness of the ensemble algorithm of SIFT and RANSAC. This application indicates the practical feasibility of feature-based algorithm and image processing technique in forensic science.

Improving stomach content based death time determination by maximum probability estimation

Stomach content based death time estimation (SCE), is a well-known technique in forensic sciences. Among more qualitatively oriented approaches the content percentage based method SCE by Tröger, Baur and Spann yields quantitative results and gives stochastic error measures for its outputs. This is possible since the methods estimator, which we call transformed expectation estimator (TEE) as well as the probability distribution of the time between last meal and death are determined numerically, though in SCE the estimator and confidence intervals are presented graphically only.Our articles outcomes are:-Explicit formulae of the TE estimator for SCE and of its probability distribution-Introduction of the maximum probability estimation (MPE) concept as well as of a MP estimator formula for SCE-Evidence that TEE>MPE, that the difference is more than ca.15% of the TEE and the difference can rise up to ca. 1h-Evidence that MPE is more relevant in forensic contexts than TEE

Building a Professional Profile: Charles Dickens and the Rise of the “Detective Force”

Building a Professional Profile: Charles Dickens and the Rise of the “Detective Force”

The logical foundations of forensic science: towards reliable knowledge.

The generation of observations is a technical process and the advances that have been made in forensic science techniques over the last 50 years have been staggering. But science is about reasoning-about making sense from observations. For the forensic scientist, this is the challenge of interpreting a pattern of observations within the context of a legal trial. Here too, there have been major advances over recent years and there is a broad consensus among serious thinkers, both scientific and legal, that the logical framework is furnished by Bayesian inference (Aitken et al. Fundamentals of Probability and Statistical Evidence in Criminal Proceedings). This paper shows how the paradigm has matured, centred on the notion of the balanced scientist. Progress through the courts has not been always smooth and difficulties arising from recent judgments are discussed. Nevertheless, the future holds exciting prospects, in particular the opportunities for managing and calibrating the knowledge of the forensic scientists who assign the probabilities that are at the foundation of logical inference in the courtroom.

Possibilities of Thermal Analysis for the Evaluation of Construction Materials

The article deals with the use of thermal analysis as an effective tool for the evaluation of building materials. The applied method of combined DSC/TG analysis is briefly described. Its utilization is illustrated by analyzing a sample of carbonated concrete. The method has wide application in other sectors, including analysis techniques in forensic science.

Editorial

Welcome to this special edition of X-ray spectrometry in forensics! The X-ray spectrometry technique scanning electron microscope energy dispersive X-ray analysis (SEM-EDS) is widely used by forensic laboratories for the examination of trace evidence. The technique is used in the international standard for gunshot residue analysis and is also used for the analysis of fibres, hair, glass and paint specimens, to name a few. The technique has gained increasing popularity since the 1970s because of its low cost, non destructive nature, ease of operation and interpretation. In this edition, we will see how complementary X-ray spectrometry methods may assist the forensic investigations of the future. In particular, Galli et al. show how portable X-ray fluorescence (XRF) devices are used in the related field of cultural heritage and how some of the advantages of portable XRF might be translated to forensic samples. On this theme, Fonseca et al. will show how XRF can be used to estimate shooting distance, and Ernst et al. outline a protocol for forensic glass analysis by using XRF. On a larger scale to tube XRF, synchrotron XRF (SXRF) has been recently used in a murder case in Japan, and Kawai gives an interesting account of the Jury's interpretation of the SXRF data from two experts, adding his own interpretation to the data, highlighting the complexity of interpretation of XRS spectra in a forensic context. Nakai et al. will show how a soil database is being constructed in Japan by using SXRF, outlining a new and useful application of the technique in forensic science. As SEM-EDS is a noteworthy force in forensics, optimisation and modification of the technique are essential to meet increasing demands from police organisations for high throughput, low cost and robust analytical techniques. Levin et al. meet these demands in the context of high throughput gunshot residue analysis by capitalising on new developments in instrumentation. Their article provides a guide, which will be useful for other forensic laboratories interested in installing silicon drift detectors. In complement to this article, French et al. use SEM-EDS to look at the possibility of secondary transfer of gunshot residue under various circumstances, putting the spotlight on the interpretation of gunshot residue evidence in the courts. It is evident from this edition that X-ray spectrometry techniques have a great range of potential and exciting new applications, which could have a significant impact on police investigations.

Facial soft tissue thickness of Colombian adults

Facial reconstruction is a widely used technique in forensic sciences to identify human bone remains and, for such, it is necessary to be aware of the values of facial soft tissue thickness characteristic for each population group. In Colombia, no conclusive values exist regarding facial soft tissue thickness for populations of mixed racial origin that also consider the nutritional state. The study used images from 30 live subjects from both genders, 26 males and four females, age range from 18 to 35 years, The images were obtained through cone beam computed tomography in mestizo population from the city of Cali (Colombia), taken in sitting position and 0.3mm resolution. The height and weight of all subjects were determined and their body mass index (BMI) was calculated. Seventeen facial thicknesses were measured over the corresponding anatomical landmarks of the skull. No significant difference was found associated to gender for most anatomical landmarks. However, where differences were found, these were mainly located on the anatomical landmarks of the medial line and particularly with greater value among males. Differences were observed in thicknesses for Colombian population when compared to other studies. The values of facial thickness characterize the Colombian population of mixed racial origin and permit greater approximation in facial reconstructions with forensic purposes.

Advice for the Courts? Sufficiently Reliable Assistance with Forensic Science and Medicine (Part 2)

In recent years, following public inquiries (for example, the Goudge Inquiry, 2007–08), reviews (for example, the US National Academy of Science, 2009; the Law Commission of England and Wales, 2011), systematic analysis of wrongful convictions (for example, Innocence Projects) and empirical studies, weaknesses with many types of forensic science and the frailty of the adversarial criminal trial have been exposed, though inadequately addressed. Drawing upon emerging empirical evidence from a variety of common law jurisdictions (and recent work in the sociology of science) and building upon the discussion of the Law Commission's Report and draft Bill (in Part 1), this article considers one means of helping common law courts to respond to some of the primary difficulties raised by incriminating forensic science and forensic medicine evidence. The proposal, involving an independent multidisciplinary advisory panel (or MAP) reviewing impugned forensic science and medical techniques to assess their reliability in order to provide support with admissibility determinations, is intended to provide practical assistance with controversial expert opinion evidence adduced by the state though without excessive encroachment upon the traditional party-dominated accusatorial trial.

Use of Forensic Science in Investigating Crimes of Sexual Violence

This article contrasts the theoretical potential of modern forensic science techniques in the investigation of sexual violence cases with empirical research that has assessed the role played by scientific evidence in the criminal justice processing of sexual assault cases. First, the potential of forensic scientific procedures (including DNA testing) are outlined and the sexual assault literature that examines the importance of physical and forensic evidence in resolving such cases is reviewed. Then, empirical data from a recent National Institute of Justice (NIJ) study of 602 rapes are presented that describe the forensic evidence collected and examined in such cases and its impact on decisions to arrest, prosecute, adjudicate, and sentence defendants. The article closes with a discussion of research and policy recommendations to enhance the role played by forensic science evidence in sexual assault investigations.

BIOTERROR THREAT SEEN AS GROWING

TEN YEARS AFTER a series of anthraxlaced letters killed five people and alerted America to the risks posed by bioterrorism, the country is still not adequately prepared for a large-scale terrorist attack using a biological weapon, federal officials and biosecurity experts warn. The U.S. has spent more than $65 billion on biodefense-related activities since 2001, Sen. Joseph I. Lieberman (I-Conn.), chairman of the Senate Homeland Security & Governmental Affairs Committee, noted at a hearing last month. “Really we’ve done a lot more than the average American knows about to protect their security,” Lieberman remarked. Firstresponder capabilities have been strengthened, new vaccines have been developed, and forensic science techniques have improved, he said. “But it is also clear from reports that we are not prepared for a catastrophic biological incident,” Lieberman pointed out. The nation is better prepared for a small-scale attack, but gaps remain there, too, he acknowledged. “We lack a strategy for dispen...

The Genetics of Innocence: Analysis of 194 U.S. DNA Exonerations

This new analysis of 194 DNA exonerations, representing 171 criminal events, examines the types of evidence and DNA testing that have been used to free the victims of wrongful conviction. The types of DNA testing used to free the innocent parallels the growth of these techniques in forensic science. Short tandem repeat (STR) analysis now prevails (70%), though Y-STR analysis (16%) and mitochondrial testing (10%) are still used when STR analysis is not feasible, and the recently developed mini-STRs have been used for exonerations since 2008 (2.6%). The types of exculpatory evidence included intimate swabs (65%), clothing (53%), hair (13%), fingernail evidence (5%), cigarettes (3%), and other evidence. The most common factor associated with wrongful convictions was misidentification (75%), including misidentification by the victim (65%). False confessions (including admissions and pleas) were obtained in 30% of the cases, and informant testimony (including jailhouse and government informants) was used in 22% of the false convictions. Several types of invalid forensic science testimony were used to wrongfully convict in the 146 trials where transcripts or reliable forensic science data were available for analysis. Invalid testimony included serology (38%), hair comparison (22%), fingerprint comparison (2%), and bite mark comparison (3%). In 43% of the exonerations, the true perpetrator of the crime was identified through postconviction testing.

Surface analysis techniques in forensic science

Surface science techniques are a suite of analytical methods that can be used to analyze the surfaces of materials. There are a host of techniques available, including Mass Spectrometry, X ray Spectrometry and Infra-red Spectroscopy which all give complementary information about the surface of the sample in question. In this special edition, we’ve extended the remit of the journal to include an array of analytical techniques which are not necessarily so surface specific, for example accelerator mass spectrometry (AMS) and particle induced X ray emission (PIXE), but provide valuable complementary information about the samples. How Do Surface Science Techniques Assist the Forensic Practitioner?

Multiple isotope forensics of nitrate in a wild horse poisoning incident

Multiple stable isotope analysis can be a powerful technique in forensic sciences. Oxygen and nitrogen isotopes were used to determine the source of nitrate that was responsible for the poisoning deaths of 71 wild horses in the Nevada desert. The nitrate was present in a water-filled hole known as ‘the Main Lake depression.’ Nitrate from the Main Lake depression had δ 18O and δ 15N values that were very positive (+32‰, +37‰), and Δ 17O values of approximately +2‰. The isotopic data suggested that the most probable source of the nitrate was nitrification of nitrogen from horse manure and urine that had leached into the pond. The δ 18O signal suggested that extreme evaporative concentration had occurred, resulting in toxic levels of nitrate accumulating in the Main Lake depression. The study demonstrates the utility of the multiple stable isotope analysis approach for characterizing sources of nitrate.

Wildlife forensics: “Supervised” assignment testing can complicate the association of suspect cases to source populations

Forensic science techniques are an important component of investigations for wildlife-related offences. In particular, DNA analyses can be used to characterize several attributes of biological evidence including sex, individual and species identification. Additionally, genetic assignment testing has enabled forensic biologists to identify the local population from which an individual may have originated. This technique has proved useful in situations where animals have been illegally harvested from areas/populations where hunting is prohibited. For this report, we used individual-based clustering (IBC), in the program Structure 2.2, under both “supervised” and “unsupervised” approaches to assess whether three suspected, illegally harvested moose originated from an endangered population. Atypical circumstances, with Nova Scotia having two moose sub-species in its jurisdiction, enabled strong IBC assignment testing results to determine the source population of the suspected samples. We found differences between the “unsupervised” and “supervised” modeling approaches to define genetic structure among the a priori characterized populations in our data set. Our findings illustrate the fact that individual clustering assignment tests can assist wildlife forensic cases to identify the source population of illegally harvested animals. However, the accuracy of results are highly dependant on the model choice used to define genetic clusters, as well as on the availability of a thorough database of samples throughout the managed area to accurately identify all genetic populations. Further, it is clear from our analyses that political jurisdictions do not accurately reflect isolated populations and we recommend using unsupervised IBC modeling for biological accuracy.

Of Black Boxes, Instruments, and Experts: Testing the Validity of Forensic Science

ABSTRACTThis paper argues that judges assessing the scientific validity and the legal admissibility of forensic science techniques ought to privilege testing over explanation. Their evaluation of reliability should be more concerned with whether the technique has been adequately validated by appropriate empirical testing than with whether the expert can offer an adequate description of the methods she uses, or satisfactorily explain her methodology or the theory from which her claims derive. This paper explores these issues within two specific contexts: latent fingerprint examination and the use of breath tests for the detection of alcohol. Especially in the forensic science arena, I suggest courts have often been seduced by superficially plausible explanations and descriptions of a technique or method, and permitted these to serve as a substitute for empirical testing. Thinking through these two examples illustrates both why evaluating the extent of testing should be the most important method by which courts assess reliability, and why, when other forms of explanatory evidence are readily available, we may nonetheless elect to make use of them. This paper suggests that these descriptions and explanations may at times usefully supplement evidence of testing, but should not generally be substituted for it. Finally, this paper embraces a kind of evidentiary pragmatism, in which the quantum of evidence required to establish legal reliability is determined not in the abstract, but in relation to the evidence that is, or ought to be, available as a result of reasonable research and investigation.

The Relationship Between the Detection of Acquisitive Crime by Forensic Science and Drug‐Dependent Offenders

Drug- and nondrug-related acquisitive crime offences such as burglary, theft, and motor vehicle theft, were compared to assess whether drug abusers were more likely to be apprehended via forensic science techniques. Data were all acquisitive offences committed over a 6-year period within a police force area in England. Drug-dependent offenders committed a wider range of offence types than nondependent offenders, and they were significantly more likely to be detected via their DNA or fingerprints (p < 0.01). A logistic regression (n > 14,000) revealed a number of predictors that influence the detection of the crime by forensic techniques. The results indicate that a number of these predictors are of statistical significance; the most significant of these being drug use by the offender with sex, ethnicity, and employment status also being relevant. Age of the offender and number of offences committed were found not to be significant. Of the four hypotheses considered to explain this, the most likely was thought to be the physical and mental impact of drug use on crime scene behavior. Consideration is given to the disciplines of forensic science and forensic psychology working closely together to distinguish factors that influence crime scene behavior.

The Development and Application of a Diatom‐Based Quantitative Reconstruction Technique in Forensic Science

Diatoms are a group of unicellular algae that have been recorded and classified for over 200 years and have been used in a range of applications in forensic science. We have developed a quantitative diatom-based reconstruction technique to confirm drowning as a cause of death and localize the site of drowning in two recent, high-profile, case studies. In both case studies we collected diatom samples from the local and/or regional area to act as a control in the examination of diatom assemblages associated with lungs and clothing. In Case Study 1 the modern analog technique suggested that all lung and clothing samples have statistically significant similarities to control samples from shallow water habitats. In Case Study 2, the analog matching suggested that the majority of lung samples show a statistically significant relationship to samples from a pond, indicating that this was the drowning medium.

Radiographic Human Identification Using Bones of the Hand: A Validation Study

The 1993 Supreme Court case Daubert v. Merrell-Dow Pharmaceuticals, Inc. underscores the importance of validating forensic science techniques. This research examines the validity of using posterior-anterior radiographs of the hand to make positive identifications of unknown human remains. Furthermore, this study was constructed to satisfy the requirements of Daubert's guidelines of scientific validity by establishing a standard methodology for hand radiograph analysis, testing the technique, and noting rates of error. This validation study required twelve participant examiners from the forensic science community, working independently, to attempt to match 10 simulated postmortem radiographs of skeletonized hands to 40 simulated antemortem radiographs of fleshed cadaver hands. The overall accuracy rate of the twelve examiners was 95%, while their collective sensitivity and specificity were 95% and 92%, respectively. However, the accuracy of each examiner was related to the amount of radiological training and experience of the observer. Six Ph.D. forensic anthropologists and four experienced forensic anthropology graduate students correctly identified all the matches. Participant examiners noted bone morphology, trabecular patterns of the proximal and middle phalanges, and distinctive radiopaque and radiolucent features as the anatomical features that aided the identification process. The hand can be an important skeletal element for radiographic positive identification because it contains 27 individual bones for comparative analysis.