Particle size analysis of soils under simulated scene of crime conditions: the interest of multivariate analyses

Two simulated scenes of crime have been studied. Soil traces adhering to boots, sport shoes and tissues have been compared with control samples using particle size analysis. Comparisons of percentage of particles per class interval and multivariate analyses were used to determine how the size distribution of each suspect sample varied compared to the original distribution. A loss of coarse fractions characterized most of the suspect samples even though they were derived from soils having different distributional patterns. However, the differences between control and suspect samples were found to be more important for soils dominated by extreme size classes than for soils rich in medium size particles. The differences among soil samples from the same source were found to be restricted to the extreme size classes. The finding of significant differences within size classes ranging from 1 to 0.063 mm should be then considered as a dissimilarity sign between trace sample and hypothetic control soil.     

Particle size analysis of soils under simulated scene of crime conditions: the interest of multivariate analyses

Two simulated scenes of crime have been studied. Soil traces adhering to boots, sport shoes and tissues have been compared with control samples using particle size analysis. Comparisons of percentage of particles per class interval and multivariate analyses were used to determine how the size distribution of each suspect sample varied compared to the original distribution. A loss of coarse fractions characterized most of the suspect samples even though they were derived from soils having different distributional patterns. However, the differences between control and suspect samples were found to be more important for soils dominated by extreme size classes than for soils rich in medium size particles. The differences among soil samples from the same source were found to be restricted to the extreme size classes. The finding of significant differences within size classes ranging from 1 to 0.063 mm should be then considered as a dissimilarity sign between trace sample and hypothetic control soil.     

The use of the M-Vac® wet-vacuum system as a method for DNA recovery

Collecting sufficient template DNA from a crime scene sample is often challenging, especially with low quantity samples such as touch DNA (tDNA). Traditional DNA collection methods such as double swabbing have limitations, in particular when used on certain substrates which can be found at crime scenes, thus a better collection method is advantageous. Here, the effectiveness of the M-Vac® Wet-Vacuum System is evaluated as a method for DNA recovery on tiles and bricks. It was found that the M-Vac® recovered 75% more DNA than double swabbing on bricks. However, double swabbing collected significantly more DNA than the M-Vac® on tiles. Additionally, it was found that cell-free DNA is lost in the filtration step of M-Vac® collection. In terms of peak height and number of true alleles detected, no significant difference was found between the DNA profiles obtained through M-Vac® collection versus double swabbing of tDNA depositions from 12 volunteers on bricks. The results demonstrate that the M-Vac® has potential for DNA collection from porous surfaces such as bricks, but that alterations to the filter apparatus would be beneficial to increase the amount of genetic material collected for subsequent DNA profiling. These results are anticipated to be a starting point to validate the M-Vac® as a DNA collection device, providing an alternative method when DNA is present on a difficult substrate, or if traditional DNA collection methods have failed.     

Comparison of the variables affecting the recovery of DNA from common drinking containers

As the boundaries of forensic DNA profiling continue to expand, less obvious sources of biological evidence are being collected at crime scenes for DNA profiling. One example is the recovery of biological evidence from common drink containers, such as bottles and cans, which have been found at crime scenes. There are many variables that may have an impact on recovering a DNA profile from such exhibits. In this research, the effects of person to person variation, time, type of drink (including alcoholic and non-alcoholic beverages), and type of drink container, were assessed for their impact on the major analytical outcomes of the DNA process. The results show that the alpha-amylase activity varies from individual to individual and is reduced in the presence of some alcoholic drinks. A reasonable DNA yield was obtained from all samples, however, the concentrations exhibited significant person to person variation. The type of drink container influenced the DNA yield with cans giving a higher yield than bottles of the same drink type. To a reduced extent the presence or absence of alcohol affected the overall DNA yield and when partial or failed DNA profiles were produced they were more likely to be associated with alcoholic drinks than non-alcoholic drinks.     

The use of simulated crime scenes in teaching undergraduate forensic sciences: Implementing an active learning approach to forensics

Incorporating a simulated crime scene into one’s pedagogy in forensic science undergraduate courses allows students the opportunity to experience a realistic scenario while demonstrating their knowledge and enhancing their critical thinking skills. The purpose of this paper is to examine an active learning approach to using simulated crime scenes to provide an impactful learning experience for students. While potentially challenging for the instructor, constructing a crime scene scenario can provide students with hands-on practical experience while helping to dispel forensic science misconceptions. Through many years of creating crime scenes, best practices for using such high impact activities in forensic science courses are described in detail, including preparatory exercises that culminate in the final crime scene scenario, considerations in preparing and constructing a crime scene activity, and supervising and assessing students once the activity begins. Three major challenges to implementing active learning exercises such as simulated crime scenes in undergraduate forensic science programs include high workload for instructors, limited supplies, and lack of suitable facilities. Workload solutions include instructors and departments considering the cost and benefit of course releases to improve curriculum and student enrollment. Supplies and facilities solutions involve innovation in reuse and repurposing of supplies, and instructor flexibility in using classroom and outdoor spaces.     

Experimental forensic scenes for the characterization of ground-penetrating radar wave response

Over the last few decades, the use of non-intrusive geophysical techniques, which allows for coverage of an entire crime scene in a reasonable amount of time, in forensic investigation has increased. In this study, we analyze the effectiveness of ground-penetrating radar (GPR) in forensics. Experimental scenes were simulated and some of the most commonly buried items in actual crime scenes were introduced, such as bone remains, guns and drug caches. Later, a GPR survey was conducted on the experimental grids with a 500 MHz antenna. The final purpose was to characterize the radar wave response expected for each set of remains to assist with its identification in later actual investigations. The results collected provided promising information that can be used when surveying real cases. Nevertheless, there were some interpretational difficulties regarding the sizes of the items and the electromagnetic properties of the materials. For these cases, finite-difference time-domain modeling was employed to achieve an advanced interpretation of the field data. The simulated models used were built from accurate geometric data provided by photogrammetric methods, which replicate the experimental scenes in fine detail. Furthermore, this approach allowed for the simulation of more realistic models, and the synthetic data obtained provided valuable information for assisting in the interpretation of field data. As a result of this work, it was concluded that GPR can be an effective tool when searching for a variety of materials during a crime scene investigation.     

Use of footwear impressions in crime scene investigations assisted by computerised footwear collection system

Crime scene footwear classification systems can be utilized to look for possible suspects, to get models and brand names for crime scene impressions and to link crime scenes. In this work a computerised footwear classification system is presented. The classification coding of the system has been designed especially for partial footwear impressions which are the most typical in crime scenes. The system is flexible because it is possible to agree within a crime scene investigation unit the way in which the system is to be applied. If outsole patterns are classified accurately in processing for the database, time will be saved in the search process and vice versa. The accurate classification coding is propounded by the fact that only a few experienced users are needed to perform the classification and data storage and all police officers returning from crime scenes are able to perform searches very easily. The users only have to follow the defined rules for geometric shapes. The crime scene investigation unit of the Turku police tested the system for a period of 1.5 years. The system has proved to be of valuable assistance in investigation when several of the hints lead to early solving of a crime. Practical experiences are described.     

The Spatial Distribution of Postblast RDX Residue: Forensic Implications

Locating exactly where trace explosive residue samples should be sought during sample collection at bomb scenes is not specified in the published literature or guidelines; in this area, it is generally acknowledged that forensic practices are based on tradition rather than evidence. This study investigated patterns in the spatial distribution of postblast 1,3,5‐trinitro‐1,3,5‐triazocyclohexane residue from a series of unconfined detonations, over a range of sampling sites, and at two different detonation heights. The amount of residue recovered from the sites decreased as a function of distance from the center of the explosion. [Correction added after online publication 27 December 2012: In the preceding sentence, “increased” was corrected to “decreased” to agree with the conclusion of the article.] As the height of the detonations increased, more residues were found from all sampling sites. The findings of this empirical study have a number of important practical implications including determining where residue samples are best sought at crime scenes.     

Comparison of quantitative PCR and culture-based methods for evaluating dispersal of Bacillus thuringiensis endospores at a bioterrorism hoax crime scene

Since the anthrax mail attacks of 2001, law enforcement agencies have processed thousands of suspicious mail incidents globally, many of which are hoax bioterrorism threats. Bio-insecticide preparations containing Bacillus thuringiensis (Bt) spores have been involved in several such threats in Australia, leading to the requirement for rapid and sensitive detection techniques for this organism, a close relative of Bacillus anthracis. Here we describe the development of a quantitative PCR (qPCR) method for the detection of Bt crystal toxin gene cry1, and evaluation of the method's effectiveness during a hoax bioterrorism event in 2009. When combined with moist wipe sampling, the cry1 qPCR was a rapid, reliable, and sensitive diagnostic tool for detecting and quantifying Bt contamination, and mapping endospore dispersal within a mail sorting facility. Results from the cry1 qPCR were validated by viable counts of the same samples on Bacillus-selective agar (PEMBA), which revealed a similar pattern of contamination. Extensive and persistent contamination of the facility was detected, both within the affected mailroom, and extending into office areas up to 30m distant from the source event, emphasising the need for improved containment procedures for suspicious mail items, both during and post-event. The cry1 qPCR enables detection of both viable and non-viable Bt spores and cells, which is important for historical crime scenes or scenes subjected to decontamination. This work provides a new rapid method to add to the forensics toolbox for crime scenes suspected to be contaminated with biological agents.     

Genetic identification of biological samples buried in clay soil during summer and winter seasons

The analysis of a biological samples found in crime scenes can be a challenging task. Minute amount of DNA, degraded DNA and the presence of inhibitors in biological samples, can interfere with the achievement of a complete genetic profile.Chelating resin, silica membranes and silica-coated with paramagnetic resin were the techniques used in this study for the isolation and purification of DNA. Our aim was to find out the best DNA extraction method for application in the presence of biological samples buried in clay soil.     

Shoeprint image retrieval and crime scene shoeprint image linking by using convolutional neural network and normalized cross correlation

A shoeprint image retrieval process aims to identify and match images of shoeprints found at crime scenes with shoeprint images from a known reference database. It is a challenging problem in the forensic discipline of footwear analysis because a shoeprint found at the crime scene is often imperfect. Recovered shoeprints may be partial, distorted, left on surfaces that do not mark easily, or perhaps come from shoes that do not transfer marks easily. In this study, we present a shoeprint retrieval method by using a convolutional neural network (CNN) and normalized cross-correlation (NCC). A pre-trained CNN was used to extract features from the pre-processed shoeprint images. We then employed NCC to compute a similarity score based on the extracted image features. We achieved a retrieval accuracy of 82% in our experiments, where a “successful” retrieval means that the ground truth image was returned in the top 1% of returned images. We also extend our shoeprint retrieval method to the problem of linking shoeprints recovered from crime scenes. This new method can provide a linkage between two crime scenes if the two recovered shoeprints originated from the same shoe. This new method achieved a retrieval accuracy of 88.99% in the top 20% of returned images.     

Human semen stain analysis in casework sample by HRM-qPCR

Determining the biological origin of body fluid evidence from crime scenes is extremely important for criminal investigation, especially in sexual assault cases. In Brazil, sexual crimes still present low-resolution rates, where approximately 8% of cases are judged. The determination of the presence of semen in samples from crime scenes as a test prior to DNA analysis is a mandatory requirement in forensic analysis and can help to better understand the dynamics of the event. This report aims to present the methodological strategy used in a criminal case of a home invasion where a t-shirt containing visible stains similar to human semen was found at the site. Convencional tests to detect the presence of PSA and sperm cells were performed on the fabric cutouts which showed negative results. We then processed the fabric samples for genetic analysis after two-years-storage, where were performed automated method for the genetic material isolation (QIAcube, Qiagen). The Real-time PCR analysis were carried out using the SOLIScript 1-step SolisGreen (SolisBiodyne) kit, with specific primers to the TGM4 (Transglutaminase 4) gene, in the Rotor Gene Q-5Plex HRM equipment (Qiagen). The results obtained for the melt curve indicated the presence of human semen in the analyzed samples. After the HRM-qPCR assay we also analyzed the a-STR and Y-STR markers. All the results were useful for the criminal process, which led to the identification of the author of the crime.     

The value of DNA material recovered from crime scenes

Abstract:  DNA material is now collected routinely from crime scenes for a wide range of offenses and its timely processing is acknowledged as a key element to its success in solving crime. An analysis of the processing of approximately 1500 samples of DNA material recovered from the property crime offenses of residential burglary, commercial burglary, and theft of motor vehicle in Northamptonshire, U.K. during 2006 identified saliva and cigarette ends as the main sources of DNA recovered (approximately 63% of samples) with blood, cellular DNA, and chewing gum accounting for the remainder. The conversion of these DNA samples into DNA profiles and then into matches with offender profiles held on the U.K. National DNA database is considered in terms of the ease with which Crime Scene Examiners can recover DNA rich samples of different sources, the location of the DNA at the crime scene, and its mobility. A logistical regression of the DNA material recovered has revealed a number of predictors, other than timeliness, that greatly influence its conversion into a DNA profile. The most significant predictor was found to be Crime Scene Examiner accreditation with offense type and DNA sample condition also being relevant. A similar logistical regression of DNA samples profiled that produced a match with an offender on the U.K. National DNA database showed no significance with any of the predictors considered.     

UNEMPLOYMENT,CRIME, AND IMPRISONMENT: A PANEL APPROACH*

Despite the widespreach acceptance of the notion that during periods of economic downturn, higher levels of unemployment lead to higher levels of crime and imprisonment, the research literature reveals very little consistent support for the existence of such a relationship. Studies that do suggest unemployment causes crime and imprisonment have used methodological techniques which, especially in over-time studies, could lead to the acceptance of spurious effects caused by trend and lag as evidence of a true relationship. Using data over a six-year period for the United States, a panel model is specified in which appropriate controls for intra-series trend and cross-series lagged effects are included. Although bivariate correlations are strongly suggestive of a relationship between unemployment and crime, results of the panel approach suggest that most of the apparent relationship is due to common trend effects. Little evidence is found for the existence of a relationship between crime/imprisonment and unemployment, regardless of the type of effect considered. In addition, results from stability tests indicate that the crime-unemployment relationship has been unstable. while the unemployment-imprisonment relationship has been relatively invariant.     

Changing Control of the Open Drug Scenes in Oslo— Crime,Welfare, Immigration Control,or a Combination?

Over the last few years there has been a societal move away from a perception of drug users as criminals to a perception of the users as sick. Contrary to what one may expect from such a change, reported drug crimes against the penal code are at record-high levels. It is the contradictory inherent in these tendencies that will be emphasized and highlighted in this article. The open drug scenes in Oslo and the police control of the scenes have changed. During the last few years there has been a growing element of foreign citizens in the drug scenes, and the police control has focused on the foreigners. Could part of the explanation of the contradictions be that there is a differentiation of how the different users are handled? Are there different forms of social control employed toward Norwegian and foreign actors in the open drug scenes? This article puts forward arguments that this is actually the case, driven by a consistent association of foreign actors in the drug scene with organized crime, and a stricter Norwegian legislation and approach to immigration questions, with a tendency toward a conflation of immigration and criminal law.     

Forensic Identification of Blood in the Presence of Contaminations Using Raman Microspectroscopy Coupled with Advanced Statistics: Effect of Sand,Dust, and Soil

Body fluid traces recovered at crime scenes are among the most common and important types of forensic evidence. However, the ability to characterize a biological stain at a crime scene nondestructively has not yet been demonstrated. Here, we expand the Raman spectroscopic approach for the identification of dry traces of pure body fluids to address the problem of heterogeneous contamination, which can impair the performance of conventional methods. The concept of multidimensional Raman signatures was utilized for the identification of blood in dry traces contaminated with sand, dust, and soil. Multiple Raman spectra were acquired from the samples via automatic scanning, and the contribution of blood was evaluated through the fitting quality using spectroscopic signature components. The spatial mapping technique allowed for detection of “hot spots” dominated by blood contribution. The proposed method has great potential for blood identification in highly contaminated samples.     

The use of Polilight in the detection of seminal fluid, saliva, and bloodstains and comparison with conventional chemical-based screening tests

Biological stains can be difficult to detect at crime scenes or on items recovered from crime scenes. The use of a versatile light source may assist in their detection. The ability of Polilight to locate potential semen, saliva, and blood stains on a range of substrates and at different dilutions was tested. We also tested the use of Polilight in comparison with conventional chemical-based presumptive screening tests such as acid phosphatase (AP), Phadebas, and luminol, often used in casework for detecting potential semen, saliva, and blood stains, respectively. The Polilight was able to locate stains that were not apparent to the naked eye. The color of the material on which a stain is deposited can have an effect on the detectibility of the stain. The Polilight was found to be comparable with the AP and Phadebas tests in terms of its sensitivity. In a comparative study between the AP test and Polilight on 40 casework exhibits, one false-negative result was observed when using the Polilight. On a series of mock casework exhibits it was determined that the Polilight can be used successfully to locate saliva stains for DNA analysis. The sensitivity of luminol for detecting potential bloodstains was greater than that of Polilight; however the Polilight has particular application in instances where a bloodstain may have been concealed with paint. Overall, the Polilight is a relatively safe, simple, noninvasive, and nondestructive technique suitable for use in forensic casework.     

Profiling the scent of weathered training aids for blood-detection dogs

At outdoor crime scenes, cadaver-detection and blood-detection dogs may be tasked with locating blood that is days, weeks or months old. Although it is known that the odour profile of blood will change during this time, it is currently unknown how the profile changes when exposed to the environment. Such variables must be studied in order to understand when the odour profile is no longer detectable by the scent-detection dogs and other crime scene tools should be implemented. In this study, blood was deposited onto concrete and varnished wood surfaces and weathered in an outdoor environment over a three-month period. Headspace samples were collected using solid phase microextraction (SPME) and analysed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC–TOFMS). The chemical odour profiles were compared with the behavioural responses of cadaver-detection and blood-detection dogs during training. Data interpretation using principal component analysis (PCA) and hierarchical cluster analysis (HCA) established that the blood odour could no longer be detected using SPME–GC×GC–TOFMS after two months of weathering on both surfaces. Conversely, the blood-detection dogs had difficulty locating the blood samples after one month of weathering on concrete and after one week of weathering on varnished wood. The scent-detection dogs evaluated herein had not been previously exposed to environmentally weathered blood samples during training. Given that this study was conducted to test the dogs' baseline abilities, it is expected that with repeated exposure, the dogs' capabilities would likely improve. The knowledge gained from this study can assist in providing law enforcement with more accurate training aids for blood-detection dogs and can improve their efficiency when deployed to outdoor crime scenes.     

Value of DNA evidence in detecting crime

DNA material is now collected routinely from crime scenes for a wide range of offences and the timely processing of the DNA is seen as key to its success in investigating and detecting crime. An analysis of DNA material recovered from the volume crime offences of residential burglary, commercial burglary, and theft of motor vehicle in Northamptonshire, U.K., in 2004 has enabled the DNA to be categorized into seven sources. Further analysis using a logistical regression has revealed a number of predictors, other than timeliness, that greatly influence whether the DNA material recovered from a crime scene enables the crime to be detected. The results indicate that a number of these predictors are of statistical significance and may be just as relevant in determining whether DNA successfully detects the crime as the timeliness of the processing of the DNA material. The most significant predictor was found to be investigating officer accreditation with location, quantity, and type of DNA material at the crime scene also being relevant. Accreditation of the Crime Scene Examiner recovering the DNA material was found not to be significant. Consideration is given to where further emphasis is needed by the U.K. police service to maximize the opportunities to detect volume crime with DNA.