假说在现场勘查中的应用

综述了假说的特征和演化过程。通过案例论述假说作为逻辑推理方法之一在现场勘查中应用于死亡方式和伪装现场等的推断常起到事半功倍的效果。从一个侧面说明,刑事技术人员的专业技术固然重要,但严密的逻辑思维同样不可缺。     

法医现场勘查学初析

法医现场勘查是公安法医检案的一个组成部分,与痕迹现场勘查各有侧重。本文通过室内、野外、运动空间三类现场初步分析了法医现场勘查的要点。     

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.     

Linking arson incidents on the basis of crime scene behavior

The present study investigated the possibility of statistically linking arson cases based on consistency of behaviors from one crime scente to another. Serial and spree arson cases were studied to differentiate underlying themes and to link cases committed by the same offender. The material consisted of 248 arson cases which formed 42 series of arsons. A content analysis using 45 dichotomous variables was carried out and principal compnents (PCA) analysis was performed to identify underlying themes. Summary scores reflecting the themes were calculated. Linking effectiveness was tested with a discriminant analysis using the summary scores. The PCA analysis was successful and underlying themes which were in accordance with previous studies could be identified. Six factors were retained, in the PCA. The linking of the arson cases was possible to a satisfactory level: 33% of the cases could be correctly linked and for over 50% of the cases, the series they actually belonged to was among the ten series identified as most probable on the basis of the linking analysis. From a practical point of view, the results could be used as a basis for developing support systems for police investigations of arson. This research was financially supported by the Finnish Ministry of Interior and by Grant 54456 from the Academy of Finland.     

基于游戏引擎的犯罪现场仿真研究

本文介绍了目前主流的可视化开发工具,结合公安实际并利用UDK（Unreal Development Kit）功能齐全,使用方便的特点,实现了犯罪现场三维重建,探讨了仿真流程、场景管理、材质及模型导入等关键问题。通过对案件模拟仿真的应用示例,将视景仿真技术与刑事科学技术紧密结合,方便了办案人员多角度观察现场、分析犯罪行为,提高了工作效率及判断的准确性,为现场勘察和重建中的技术难题寻求了解决方案。     

Identifying the scene of a crime through pollen analysis

The forensic analysis of pollen involves the comparison of crime scene and reference pollen samples. Successful matches are frequently used to solve time- or location-related crimes. Despite its prospects in criminal investigation, forensic palynology is still underused in casework due to inherent shortcomings such as its limited evidential weighting, scarcity of skilled palynologists dedicated to forensic casework and the laborious nature of analytical procedures. To address these challenges, the current state-of-the-art in forensic palynology is transiting from the traditional light microscopic methods that dominated the early days of palynology to more contemporary approaches like Raman spectroscopy, stable isotope analysis and DNA metabarcoding. The major challenges of these methods, however, include a lack of optimisation to forensic expectations and the unavailability of robust databases to permit accurate data interpretation, and quests to resolve these problems constitute the theme of current research. While reiterating the usefulness of pollen analysis in criminal investigation, this report recommends orthogonal testing as a way of improving the evidential weighting of forensic palynology.     

The persistence of fibres on skin in an outdoor deposition crime scene scenario

Textile fibres were transferred to a pig skin carcass and their persistence determined at daily intervals for up to a 12 day period during which time the carcass was left outdoors exposed to the prevailing weather conditions and animal activity. In the absence of strong winds and precipitation, the loss of fibres was found to be exponential. Stronger winds and heavier precipitation caused an increase in the rate of loss of fibres. The results of this study showed that the majority of fibres transferred to a body deposited outdoors, can be expected to be lost after the first 2 days, however, none of the experiments performed resulted in a complete loss of fibres, even after 12 days exposure. These persistence characteristics differed from those observed in a similar study using small sections of skin, rather than carcasses.The implications of the results of the present study in relation to the examination of fibre evidence in cases of homicide are discussed.     

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.     

Pollen on grass clippings: putting the suspect at the scene of the crime.

In a case of alleged sexual assault, the pollen content of samples of grass clippings and soil from the suspect's clothing and shoes was compared to that of a sample of grass clippings from the alleged crime scene (a grassy area) to determine whether or not the suspect had been at the scene. The clothing and shoe samples showed a very strong correlation with each other and with the sample from the alleged crime scene in the combination of the different types of pollen present, very strongly supporting the contention that the suspect had been at the scene.     

The place of a forensic archaeologist at a crime scene involving a buried body

This paper examines the place that forensic archaeologists should hold at scenes of crime where a body has been buried. The forensic archaeologist is rapidly becoming a key player whose specialty should be explained, and role defined. A high level of interaction between the forensic archaeologist and other personnel implies good communications skills as well as a precarious mix of receiving orders, assistance and advice as well as giving directions to other staff. The extent to which each of these should be applied will be discussed as well as underlying the absolute need for forensic archaeologist to attend these types of scenes.     

An unusual appearance of a common pollen type indicates the scene of the crime

Forensic palynology is a useful source of evidence in cases of violence committed in the open. A young girl was grabbed off the street, threatened and brutally raped. During the investigation the exact place of the rape became an issue. Growing around the scene identified by the victim were shrubs identified as Coprosma, a common New Zealand plant and one that produces abundant, easily wind-dispersed pollen. Abundant Coprosma pollen was found at the scene. The pollen were unusual in that the site was very damp, encouraging fungal growth, and fungal hyphae had penetrated the pores of many of the tricolporate pollen grains. Some grains had fungal spores inside. Coprosma pollen identical in preservational characteristics and morphology to those from the scene and containing fungal hyphae and spores were found in considerable numbers on the victim's clothes. This and rare Coprosma pollen grains and fungal remains recovered from vaginal swabs provided evidence that she had been at the scene where she claimed to have been raped. The diversity of pollen types recovered from the clothing in this case provides further evidence of the usefulness of clothing in picking up and retaining pollen from crime scenes and that obvious staining on clothes is not a pre-requisite for good pollen recovery. It also demonstrates the importance of collecting samples from different parts of the same garment in order to get a full picture of events since different parts of a garment can come into contact with different plants or different parts of the ground in a scuffle. It is also demonstrated that significant evidential material can be collected from the body, in this case from vaginal swabs from the victim. Forensic palynology should be considered in every case of violent assault, especially, but not exclusively, when having occurred in an open area subject to extensive pollen settlement.     

The effect of three-strikes legislation on serious crime in California

Using county-level data from California for the years 1989-2000, this study explored the effect of three-strikes legislation on serious crime. It improved on most previous research in this area by controlling for how often prosecutors charged offenders under the three-strikes statute. Preliminary findings suggested that larceny was reduced by way of deterrence resulting from three-strikes and that all index crimes were reduced by way of incapacitation. Once county-specific trends were controlled for, however, the deterrent and incapacitative effects of three-strikes legislation disappeared altogether.     

The effect of outpatient methadone maintenance treatment facilities on place-based crime

Journal of Experimental Criminology - This study evaluates the effect of outpatient methadone maintenance treatment (OMMT) facilities on crime in surrounding areas. Between 2007 and 2017 in...     

The analysis of biological samples from crime scene for a future human DNA profile confrontation. Effects of presumptive test reagents on the ability to obtain STR profiles for human identification

Because of the increase of evidence of blood stains, that have been washed or cleaned in an attempt to mask the analysis of DNA profiles, there is also an increase in the use of presumptive tests on samples sent to laboratories. Some of the presumptive tests, used to identify blood and semen stains, could potentially affect the recovery of high molecular weight DNA from the samples, or extinguish them, especially those already present in small quantities. After the presumptive tests, often these samples are discarded. This study aimed to examine the possibility of obtaining a DNA profile from samples submitted for presumptive testing and cleaned with bleaches with and without chlorine. Two different protocols were conducted: (a) A unique sample of human blood in natura (5 μL), already typed through the DNA techniques with the genetic profile previously known (control), was distributed onto cotton fabrics and dried at room temperature. Four samples of fabric were macerated in saline solution and Coombs serum and then stored for three months (room temperature and freezer −20 °C). (b) Another sample of human blood, type A, in natura, already typed through the techniques of DNA (control) was used. Aliquots of 200 μL were distributed in: cotton, denim and synthetic fabric. The samples were dried at room temperature for 24 h. The blood stains in those fabrics (cotton, denim and synthetic) were then divided into three groups: unwashed, cleaned with chlorine bleach and cleaned with chlorine bleach and soap powder. The samples were again dried at room temperature for 24 h, before the use of luminol. The DNA were extracted with Chelex 100 and amplified with the Identifiler Kit (Applied Biosystems). The blood stains exposed to saline and Coombs serum had DNA profiles consistent with untreated samples (controls). This result shows that the experts should keep and store the samples treated with saline and Coombs serum for future DNA confrontation when necessary. Also discussed in this paper the pattern of blood stains after washing with bleaching solutions, as well as the quantity of DNA obtained from these samples.     

The future of forensic and crime scene science. Part II. A UK perspective on forensic science education

This paper builds on the views presented by the author at 'The Future of Forensic and Crime Scene Science Conference'. Forensic science has become an increasingly prominent area of science within the last 10 years. This increasing prominence together with popularity in the subject has seen the number of undergraduate students studying forensic science related courses at UK Universities increase rapidly in just 5 years and there are no short term signs of this trend reducing. In 2005, there were 450 courses with forensic in the title offered by higher education institutes. Although the forensic community has expressed its concern that job prospects for these students wishing to pursue careers as forensic scientists will be limited numbers of students undertaking science courses have still increased. The increase in students studying forensic science comes in an era of decreasing science numbers in higher education with the potential to produce high calibre science graduates with sought after skills in critical thinking, analysis, interpretation and communication. Technology has continued to advance at a similar pace providing those responsible for managing crime with a need and opportunity to identify and predict new and future applications of science and technology; not just in reducing and detecting crime but also in predicting how technology will be used by criminals in the future. There is therefore a need for forensic science users, providers and educators to identify the knowledge and skills required by forensic scientists and crime investigators of the future to ensure that technology continues to be used and applied to its full advantage. This provides universities an opportunity to contribute to the development of both the practice and practitioners of forensic science. This paper outlines the current issues facing universities in relation to forensic science and identifies their future role in providing high quality relevant courses for future forensic practitioners; developing current forensic practitioners through their participation in applied research, short courses, conferences and qualifications linked to professional practice; and supporting and developing the practice of forensic and crime scene science, through the identification, engagement and dissemination of pure and applied research.