Validation of Tool Mark Comparisons Obtained Using a Quantitative,Comparative, Statistical Algorithm

Abstract: A statistical analysis and computational algorithm for comparing pairs of tool marks via profilometry data is described. Empirical validation of the method is established through experiments based on tool marks made at selected fixed angles from 50 sequentially manufactured screwdriver tips. Results obtained from three different comparison scenarios are presented and are in agreement with experiential knowledge possessed by practicing examiners. Further comparisons between scores produced by the algorithm and visual assessments of the same tool mark pairs by professional tool mark examiners in a blind study in general show good agreement between the algorithm and human experts. In specific instances where the algorithm had difficulty in assessing a particular comparison pair, results obtained during the collaborative study with professional examiners suggest ways in which algorithm performance may be improved. It is concluded that the addition of contextual information when inputting data into the algorithm should result in better performance.     

Macroscopic characteristics of screwdriver trauma

The main objective of the study was to determine the type of macroscopic trauma created by a flat-tipped and a cross-tipped screwdriver. The second objective was to determine if the trauma inflicted by the two screwdrivers could be macroscopically differentiated. Three tests were conducted, each by a male volunteer. Each test consisted of 12 samples of fleshed pig ribs; six were stabbed with a flat-tipped screwdriver and the remaining six with a cross-tipped screwdriver (Phillips). Each sample received 15 stab wounds during the process. The stabbings were conducted at perpendicular and oblique angles, with fabric variables being utilized. Results illustrate two main categories of macroscopic skeletal trauma, fractures, and puncture wounds. By studying the macroscopic appearance in tandem with differing trauma frequencies, these two screwdriver types can be differentiated.     

Complex suicide: an unusual case with six methods applied

Complex suicides (CSs) are committed by using more than one method. They account for 1.5-5% of all suicides. We present a case of CSs of a 44-year-old man, found dead in the vicinity of his car, in a deserted frozen field. Police investigation excluded homicide, and no medical data confirmed mental illnesses. Autopsy revealed wrist cuts, neck cuts, acid burns in the GI tract, multiple stab wounds to the head by a screwdriver, and several uncertain signs of hypothermia. Toxicology analysis (gas chromatography-mass spectrometry) confirmed ingestion of insecticide. We concluded that stab wounds to the head were the cause of death, while external hemorrhage and hypothermia were contributing factors. This is the first case of CSs reviewed in the literature where six suicide methods were applied. This particular case is interesting because the victim used a screwdriver as a tool for inflicting stab wounds to the head, which is a rare suicidal method.     

Self-inflicted burns: the value of collaboration between medicine and law

Self-inflicted burns are rare in France, but they lead to major, often life-threatening complications. The authors reviewed medical data for patients hospitalized in a burn center from January 2004 to December 2008. Thirty-eight cases of self-inflicted burns were compared with 220 accidental burns. Women were predominantly affected (57.9%, n = 22). A psychiatric history (71%, n = 27) was more frequent in this population. The mean age of the victims was 38 years. The leading method of suicide was flame (94%, n = 36) associated with gasoline used as an accelerant (77.7%, n = 28). Mean total burn surface area (41.5%) and mortality (36.9%) were higher in the self-inflicted burn population. By recognizing epidemiological characteristics and patients at risk, we can better classify lesions related to self-immolation. It is important for the forensic physician to consult survival details to correlate these data with the results of autopsy.     

To Test or Not To Test?: The Value of Toxicology in a Delayed Overdose Death

A case demonstrating the necessity of thorough death investigation processes where toxicology plays an active role is presented. A 33‐year‐old white man presented to the emergency room in respiratory distress after an overdose episode where he was revived on the scene by fire rescue. His condition continued to deteriorate and he expired 6 days after the initial incident. No admission specimens were available for testing; however, there were specimens drawn 4 and 5 days after the incident. Drug paraphernalia from the scene was obtained by the laboratory through collaboration with local law enforcement. Drug paraphernalia was initially tested in the laboratory and after obtaining the results, the antemortem and postmortem specimens were tested identifying mitragynine and U‐47700, among other drugs. These results indicate the value in obtaining and testing drug paraphernalia, and the value of testing antemortem specimens even in the event of a delay.     

Sequential monitoring of burials containing small pig cadavers using ground penetrating radar

Ground-penetrating radar (GPR) was used to monitor 12 pig burials in Florida, each of which contained a small pig cadaver. Six of the cadavers were buried in sand at a depth of 0.50-0.60 m, and the other six were buried in sand at a depth of 1.00-1.10 m to represent deep and shallow burials that are generally encountered in forensic scenarios. Four control excavations with no pig interment were also constructed as blank graves and monitored with GPR. The burials were monitored for durations of either 13 or 21 months, and were then excavated to correlate the decomposition state of the cadaver with the GPR imagery. Overall, this study demonstrated that it may be difficult to detect small cadavers buried in sand soon after they are skeletonized because the area surrounding the body, or the grave, may not provide a strong enough contrasting area to be detected by GPR when compared to that of the surrounding undisturbed soil. Also, depth of burial appears to influence grave detection because bodies that are buried at deeper depths may be detected for a longer period of time due to reduced decomposition rates.     

公安机关电子数据司法鉴定的现状与挑战

电子数据取证是信息时代公安机关重要的基础工作,是打击涉及互联网各类违法犯罪的“杀手锏”。电子数据鉴定是公安机关电子数据取证工作的重要组成部分,起到最终判定案(事)件性质,为侦查与诉讼提供依据的重要作用。公安机关电子数据鉴定与信息技术共同飞速发展,其领域不断延伸扩展、技术要求越来越高,面对的挑战也越来越多。概要介绍了公安机关电子数据鉴定的法律要求、鉴定资质、鉴定流程等内容,阐述了其面临的挑战。     

Root Morphology and Anatomical Patterns in Forensic Dental Identification: A Comparison of Computer‐Aided Identification with Traditional Forensic Dental Identification*

Abstract: An online forensic dental identification exercise was conducted involving 24 antemortem–postmortem (AM–PM) dental radiograph pairs from actual forensic identification cases. Images had been digitally cropped to remove coronal tooth structure and dental restorations. Volunteer forensic odontologists were passively recruited to compare the AM–PM dental radiographs online and conclude identification status using the guidelines for identification from the American Board of Forensic Odontology. The mean accuracy rate for identification was 86.0% (standard deviation 9.2%). The same radiograph pairs were compared using a digital imaging software algorithm, which generated a normalized coefficient of similarity for each pair. Twenty of the radiograph pairs generated a mean accuracy of 85.0%. Four of the pairs could not be used to generate a coefficient of similarity. Receiver operator curve and area under the curve statistical analysis confirmed good discrimination abilities of both methods (online exercise = 0.978; UT‐ID index = 0.923) and Spearman’s rank correlation coefficient analysis (0.683) indicated good correlation between the results of both methods. Computer‐aided dental identification allows for an objective comparison of AM–PM radiographs and can be a useful tool to support a forensic dental identification conclusion.