“Blood,Bucks and Bias”: Reliability and biasability of crime scene investigators’ selection and prioritization of blood traces

When crime scene investigators (CSIs) encounter crime scenes with large volumes of blood, some selection and prioritization is often needed, and this will impact on what blood is and is not available for forensic analysis. What factors influence CSIs decision making process is largely unknown. This study examines the effects of awareness of limited resources and irrelevant contextual case information indicating either a homicide or a suicide on CSIs collection of blood traces. To this end, two scenario-based experiments with CSIs and novices were conducted. Overall, the results suggest that even when CSIs decisions are made under identical conditions, their trace selection varies both when it comes to numbers and locations. Furthermore, awareness of limited resources made CSIs collect fewer traces and their selections also varied following the contextual case information, showing similarities and differences with novices. Since blood traces can be used to establish both activity and identity the findings can have important implications for the subsequent investigation as well as trial.     

The Forensic Confirmation Bias: A Comparison Between Experts and Novices

A large body of research has described the influence of context information on forensic decision‐making. In this study, we examined the effect of context information on the search for and selection of traces by students (N = 36) and crime scene investigators (N = 58). Participants investigated an ambiguous mock crime scene and received prior information indicating suicide, a violent death or no information. Participants described their impression of the scene and wrote down which traces they wanted to secure. Results showed that context information impacted first impression of the scene and crime scene behavior, namely number of traces secured. Participants in the murder condition secured most traces. Furthermore, the students secured more crime‐related traces. Students were more confident in their first impression. This study does not indicate that experts outperform novices. We therefore argue for proper training on cognitive processes as an integral part of all forensic education.     

DNA in the Criminal Justice System: The DNA Success Story in Perspective,

Current figures on the efficiency of DNA as an investigative tool in criminal investigations only tell part of the story. To get the DNA success story in the right perspective, we examined all forensic reports from serious (N = 116) and high‐volume crime cases (N = 2791) over the year 2011 from one police region in the Netherlands. These data show that 38% of analyzed serious crime traces (N = 384) and 17% of analyzed high‐volume crime traces (N = 386) did not result in a DNA profile. Turnaround times (from crime scene to DNA report) were 66 days for traces from serious crimes and 44 days for traces from high‐volume crimes. Suspects were truly identified through a match with the Offender DNA database of the Netherlands in 3% of the serious crime cases and in 1% of the high‐volume crime cases. These data are important for both the forensic laboratory and the professionals in the criminal justice system to further optimize forensic DNA testing as an investigative tool.     

Decision support for using mobile Rapid DNA analysis at the crime scene

Mobile Rapid DNA technology is close to being incorporated into crime scene investigations, with the potential to identify a perpetrator within hours. However, the use of these techniques entails the risk of losing the sample and potential evidence, because the device not only consumes the inserted sample, it is also is less sensitive than traditional technologies used in forensic laboratories. Scene of Crime Officers (SoCOs) therefore will face a ‘time/success rate trade-off’ issue when making a decision to apply this technology.In this study we designed and experimentally tested a Decision Support System (DSS) for the use of Rapid DNA technologies based on Rational Decision Theory (RDT). In a vignette study, where SoCOs had to decide on the use of a Rapid DNA analysis device, participating SoCOs were assigned to either the control group (making decisions under standard conditions), the Success Rate (SR) group (making decisions with additional information on DNA success rates of traces), or the DSS group (making decisions supported by introduction to RDT, including information on DNA success rates of traces).This study provides positive evidence that a systematic approach for decision-making on using Rapid DNA analysis assists SoCOs in the decision to use the rapid device. The results demonstrated that participants using a DSS made different and more transparent decisions on the use of Rapid DNA analysis when different case characteristics were explicitly considered. In the DSS group the decision to apply Rapid DNA analysis was influenced by the factors “time pressure” and “trace characteristics” like DNA success rates. In the SR group, the decisions depended solely on the trace characteristics and in the control group the decisions did not show any systematic differences on crime type or trace characteristic.Guiding complex decisions on the use of Rapid DNA analyses with a DSS could be an important step towards the use of these devices at the crime scene.     

Visualization of Latent Blood Stains Using Visible Reflectance Hyperspectral Imaging and Chemometrics

The detection of latent traces is an important aspect of crime scene investigation. Blood stains on black backgrounds can be visualized using chemiluminescence, which is invasive and requires a darkened room, or near-infrared photography, for which investigators need to change filters manually to optimize contrast. We demonstrated the performance of visible reflectance hyperspectral imaging (400–720 nm) for this purpose. Several processing methods were evaluated: single wavelength bands, ratio images, principal component analysis (PCA), and “SIMPLe-to-use Interactive Self-modeling Mixture Analysis” (SIMPLISMA). Using these methods, we were able to enhance the contrast between blood stains and 12 different fabrics. On black cotton, blood dilutions were visible with a minimal concentration of 25% of whole blood. The hyperspectral camera system used in this study is portable and wireless, which makes it suitable for crime scene use. The described technique is noncontact and nondestructive, so all traces are preserved for further analysis.     

Expanding forensic science through forensic intelligence

Research and Development (‘R&D’) in forensic science currently focuses on innovative technologies improving the efficiency of existing forensic processes, from the detection of marks and traces at the scene, to their presentation in Court. R&D approached from this perspective provides no response to doubts raised by recent criminological studies, which question the effective contribution of forensic science to crime reduction, and to policing in general.Traces (i.e. forensic case data), as remnants of criminal activity are collected and used in various forms of crime monitoring and investigation. The aforementioned doubts therefore need to be addressed by expressing how information is conveyed by traces in these processes. Modelling from this standpoint expands the scope of forensic science and provides new R&D opportunities. Twelve propositions for R&D are stated in order to pave the way.     

浅议模拟画像在侦查中的应用

模拟画像是实现对犯罪嫌疑人相貌视觉形象刻画的技术手段。模拟画像应成为犯罪现场勘查工作的一项基本的规范性内容。模拟画像技术要求勘查现场的应解决的主要问题和勘查重点有:(一)寻找、发现目击犯罪嫌疑人的受害人和其他证人;(二)访问、记录目击者对犯罪嫌疑人的感知过程;(三)提取、记录目击者对犯罪嫌疑人体貌特征的记忆;(四)对目击者的调查访问要讲究技巧。模拟画像在侦查中运用应注意的问题:(一)相貌学知识非常重要;(二)必须注意目击者的个体差异对模拟画像的影响;(三)证人之间不要有互相影响的情况;(四)对重要目击者的保护;(五)必要时重新进行模拟画像;(六)划定侦查范围非常重要;(七)可以确定犯罪嫌疑人,不能否定犯罪嫌疑人。     

Artifacts Caused by Leaf-Cutting Ants of the Genus Atta (Hymenoptera: Formicidae): Postmortem Bite Injuries and the Tearing of Clothes

Ants are one of the first insects to find an exposed cadaver and can be present during all stages of decomposition. Although these organisms are not commonly used in postmortem interval estimates, they are to be taken into account on criminal investigations involving human corpses, since they can leave bite marks that can be mistaken for antemortem or perimortem injuries, which could be misleading when ascertaining the occurrence of abuse or physical altercation during a crime. A few studies report the action of ants on human cadavers and even though leaf-cutting ants of the genus Atta are frequently encountered in succession studies that use animal carcasses, there are no records of these fungus-growing species on human corpses. Atta is a genus restricted to the New World, ranging from northern Argentina to southern United States and acts as one of the most conspicuous neotropical herbivores. In this study, we report three cases of violent death that illustrate the impact of ants, especially those of the genus Atta, in a forensic setting. We compare the patterns displayed by postmortem bite injuries caused by leaf-cutter ants and other common species with less robust mandibles. We also present the capability of Atta ants to create artifacts by cutting victim’s clothes in a crime scene, contributing to the knowledge of ant-mediated confounding factors in crime scene investigation.     

Blood-spatter patterns: hands hold clues for the forensic reconstruction of the sequence of events

Biologic and nonbiologic traces on the hands are of particular importance for the forensic reconstruction of shooting incidents; gunpowder residue analysis in particular helps determine whether the gunshot is close range or distant. In crime scene investigation, knowledge about the morphology of bloodstain patterns-including gunshot-related back spatter-has increased since various experimental examinations have been performed in the last years; nowadays, these traces are frequently used for forensic crime scene reconstruction. The goal of this study was to deduce the position and orientation of the hands, and therefore the firearm, according to the bloodstain patterns on the hands of the deceased. For this purpose blood-spatter stains on the hands were examined on site in 5 suicides caused by gunshot. In all cases, forensically relevant conclusions regarding forensic reconstruction were enabled through close examination of the spatter marks. Therefore, in shooting incidents, analysis and documentation of blood-spatter findings on the hands is recommended before hands are tested for gunpowder residue or wrapped for the transport of the body.     

The Role of Forensic Botany in Solving a Case: Scientific Evidence on the Falsification of a Crime Scene

Forensic botany can provide useful information for pathologists, particularly on crime scene investigation. We report the case of a man who arrived at the hospital and died shortly afterward. The body showed widespread electrical lesions. The statements of his brother and wife about the incident aroused a large amount of suspicion in the investigators. A crime scene investigation was carried out, along with a botanical morphological survey on small vegetations found on the corpse. An autopsy was also performed. Botanical analysis showed some samples of Xanthium spinosum, thus leading to the discovery of the falsification of the crime scene although the location of the true crime scene remained a mystery. The botanical analysis, along with circumstantial data and autopsy findings, led to the discovery of the real crime scene and became crucial as part of the legal evidence regarding the falsity of the statements made to investigators.     

Eyewitness Memory in Context: Toward a Taxonomy of Eyewitness Error

Although eyewitness memory and identification have captured substantial research interest in the past decades, an understanding of the types and prevalence of errors typically made by eyewitnesses is lacking. The purpose of the present research was to begin the development of a taxonomy of eyewitness error, employing standardized stimuli and established techniques. Respondents were exposed to a crime scene modeled on SWAT-training scenarios for systematically varied exposure times, and were then asked to describe what they had seen. The stimuli and questions employed were prepared with the aid of senior police field training officers. As anticipated, eyewitness performance in general was subject to a variety of inaccuracies. Physical errors, such as mistakes in the clothing or physical characteristics of the perpetrator, or in details of the environmental context, predominated. However, other less-expected errors were also observed: in relatively low numbers of cases, witnesses inferred emotional states or intent on the part of the perpetrator or victim. Some contributed wholly artificial backstories, reported the future actions of the perpetrator or victim as memories, or even inserted themselves into the scene. The pattern of results was shown to interact with exposure time, gender of the perpetrator, and the presence or absence of weapons in the scene. The results of this study are consistent with reconfigurative theory dating to Bartlett (1932), with subsequent research, and with more recent work under the aegis of Gestalt/Feature-Intensive Processing theory. These findings provide information on types and prevalence of eyewitness error which should prove useful in investigative and courtroom settings.     

The Food Preferences of the Blow Fly Lucilia cuprina Offered Human Blood,Semen and Saliva,and Various Nonhuman Foods Sources

As human DNA profiles can be obtained from blow fly artifacts, this study aimed to establish the feeding preferences of Lucilia cuprina (Wiedemann) blow flies when offered human biological fluids and nonhuman food sources. One‐day‐old and 3‐day‐old blow flies of both sexes were simultaneously offered human blood, semen and saliva, pet food, canned tuna and honey, and the number and length of visits documented over 6 h. One‐day‐old flies visited pet food and honey most often, but stayed longest on honey and semen. Three‐day‐old flies visited semen and pet food most often, and stayed longest on these food sources. Blood and saliva were the least preferred options for all flies. Overall, flies preferred dry blood and semen to the wet forms. These findings demonstrate that even when other food sources are available, flies at a crime scene may feed on human biological fluids if present, potentially transferring human DNA.     

犯罪剖绘:科学还是艺术?

犯罪剖绘(criminal profiling)为分析(连续)犯罪行为型态的技术,藉由统计技术分析潜在犯罪者、被害者与犯罪现场迹证等三者之间相互联结可能性。然犯罪剖绘技术应用至案件连结分析,可根据犯罪现场所遗留迹证(含心理迹证),预测/推论犯罪者之人口背景特征,并将这些案件之犯罪现场迹证系统化处理,建构成数据库,有助警察侦办连续型犯罪。经由案件连结分析所得证据,能否成为法庭上论罪之依据,在英美国家必须通过Frye法则与Daubert测试法则检验,即是否已经通过科学性检验,或同一学术领域同侪认可验证过程。因此,后续研究可朝更精确统计分析方法迈进,以提升案件连结分析数据库对于预测未发现犯罪者之准确率及其法庭证据力。     

Turf wars: authority and responsibility for the investigation of mass graves

Mass graves are complex products of large-scale crimes. Such scenes pose four conceptual challenges to investigators and forensic experts: the individual victim, the crime, the setting, and the statistical. Exhumation and post-mortem examination of mortal remains with associated personal and forensic evidence require integrated management of core forensic personnel including investigators, archaeologists, anthropologists, odontologists and pathologists, among whom there is overlapping expertise. The key to avoiding competition and ill-will among experts is to recognize that all such experts should be enabled to make known how their expertise matches with the temporal and spatial boundaries of victim, crime and setting. In turn, they should be apprised of where they fit into the overall judicial process and their limits within the investigation. Consequently, each expert requires access to the factual background of the case, to the site and its contents throughout the investigation. Each forensic team member has a responsibility to influence the investigation--throughout its course when possible--to make findings within their areas of expertise, and to make these available to the rest of the team so as to contribute most meaningfully to the aims of the investigation, both forensic and humanitarian. The on-site crime scene manager has an overarching role to enable integrated access to the complete scene and its contents by each forensic expert team member. In other words, the forensic scientist is given access and the ability to influence the investigation while control of evidence from the site as to identity and criminal activity are maintained by the crime scene manager. This contribution is directed at both the crime scene manager and each forensic expert; it describes the essential spatial and temporal parameters of an expert's opinion so as to encourage cooperation, and discourage conflict, within the forensic team.     

The effect of the ageing of crime scene objects on the results of scent identification line-ups using trained dogs

In a scent identification line-up, a trained dog matches the scent trace left by a perpetrator at the crime scene to the odour of a suspect in a line-up of different odours. The procedures are strictly defined and the results are routinely used by the police and as evidence in court in a number of European countries. This paper describes the effect of ageing of the odour trace collected at the crime scene on the performance of the dogs in recognising the perpetrator in a line-up. The results show that whilst the dogs perform faultlessly in matching odours collected on the same day, the results drop to a lower level and become more variable in the period studied (2 weeks to 6 months). However, the results do not show a systematic decrease in performance. A possible explanation is the development of a steady state in the glass jars containing the perpetrator odour trace after initial differential evaporation of components of the residue or break down of unsaturated components into saturated ones. Prevention of this initial change may prevent the drop in performance observed in this study, thus increasing the reliability of these scent identifications.     

现场残缺鞋印的分析与利用

在刑事案件现场残缺鞋印出现率较高,可是多种因素导致残缺鞋印的提取率和鉴定率却越来越低,使得残缺鞋印在案件侦破或诉讼过程中未发挥其应有的作用。事实上,残缺鞋印反映出的信息可以分析鞋种、刻画嫌疑人特征、识别鞋只等检验鉴定工作,根据现场残缺鞋印的形成机制,从主观和客观两方面分析了现场残缺鞋印提取和鉴定率低的原因,通过实际案例说明其在案件侦破及诉讼中发挥的特殊作用,并列举了残缺鞋印提取和检验时应注意一些问题．为现场勘验人员和检验人员提供参考。     

The Role of Forensic Botany in Reconstructing the Dynamics of Trauma from High Falls

The analysis of botanical traces can be supportive, especially when the crime scene investigation and autopsy do not provide sufficient information. This issue arises most commonly in fatal falls from height. We report the case of a man found dead below a hill. The body showed traumatic injuries from a fall. During the scene investigation, a sampling of botanical elements was carried out on three zones of the hill called the point of loss of balance, the point of fall, and the point of impact. The botanical elements collected on the three zones were compared with those found on the victim and an autopsy was performed. The botanical analysis clarified the phases of falling, as well as allowing us to reconstruct the dynamics and the accidental manner of death.     

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.     

Impairment based legislative limits for driving under the influence of non-alcohol drugs in Norway

Bloodstains at crime scenes are among the most important types of evidence for forensic investigators. They can be used for DNA-profiling for verifying the suspect's identity or for pattern analysis in order to reconstruct the crime. However, until now, using bloodstains to determine the time elapsed since the crime was committed is still not possible. From a criminalistic point of view, an accurate estimation of when the crime was committed enables to verify witnesses' statements, limits the number of suspects and assesses alibis. Despite several attempts and exploration of many technologies during a century, no method has been materialized into forensic practice. This review gives an overview of an extensive search in scientific literature of techniques that address the quest for age determination of bloodstains. We found that most techniques are complementary to each other, in short as well as long term age determination. Techniques are compared concerning their sensitivity for short and long term ageing of bloodstains and concerning their possible applicability to be used on a crime scene. In addition, experimental challenges like substrate variation, interdonor variation and environmental influences are addressed. Comparison of these techniques contributes to our knowledge of the physics and biochemistry in an ageing bloodstain. Further improvement and incorporation of environmental factors are necessary to enable age determination of bloodstains to be acceptable in court.     

现场血迹推断出血点位置的研究进展

血迹是命案现场最常见的痕迹之一,对血迹形态的分析是一种重建犯罪现场的有效方法,而根据现场血迹推断出血点位置则是血迹形态分析的主要任务之一。随着血迹研究的不断发展,出现了许多不同的方法（如传统拉线法、三角函数法、绘图法、计算机程序法、公式计算法、回归方程法等）用于推断出血点位置。通过结合国内外相关文献,对不同的方法进行了综述,以期为相关研究提供参考。