Bite marks: physical properties of ring adhesion to skin--phase 2

Abstract: Bite Marks: This study demonstrated that surface wetness was the most influential factor affecting ring adhesion to skin. Also, chemical depilatories and shaving creams were to be avoided when cleaning the skin. The second phase of this research examines the tensile stress needed to rupture the bond between TAK^® hydroplastic, three new cyanoacrylates, and pigskin with particular consideration for temperature variations. This study also considers solubility issues of different cyanoacrylates in 10% formalin. Finally, the Dorion Type V bitemark excision technique could significantly reduce the risks of tissue distortion when used in conjunction with the following methods and materials. The skin should be devoid of moisture, razor shaved, and cleaned with dishwashing detergent and 98.9% ethanol while avoiding the use of shaving creams and/or chemical depilatories where ring placement is anticipated. The use of unopened cyanoacrylate is encouraged with Permabond^® as the cyanoacrylate of choice.     

电烧伤皮肤金属元素的测定

本实验系用220V交流电源和直径2.0mm紫铜线为接触电极,在新鲜尸体腹部皮肤上做电烧伤实验。用原子吸收分光光度计对电烧伤皮肤中铜元素含量进行测定。结果表明电烧伤皮肤铜元素含量最高可达137.90μg/g。经10%福尔马林溶液固定40天以上的电烧伤皮肤铜元素含量有昕降低,但仍较正常皮肤含量为高。电烧伤皮肤铜元素含量以电流斑处为最高。本实验为电烧伤皮肤金属元素的定性与定量分析,检材的提取和处理,提供了一个较好的方法,有利于判定案件的性质和确定接触电极的金属种类。     

不同环境条件下大鼠死后皮肤生物力学特性改变

目的死亡时间的推测是法医病理学研究的重点和难点。皮肤具有一定生物力学特性,是机体死后分解破坏发生较迟的部分。本研究观察不同环境条件下死后大鼠皮肤生物力学特性的改变,探索其与死亡时间的关系。方法系统测试雌性SD大鼠在不同环境条件下（A组较高环境温度,B组较低环境温度）的死后皮肤生物力学特性。结果 A组大鼠皮肤死后张应力、延伸率在死后1d内先降低后升高,1d～6d逐渐降低,6d～7d略呈上升趋势;B组大鼠皮肤死后张应力在死后2d内先降低后升高,2d～16d逐渐降低,16d～20d略上升。结论 A组的张应力、延伸率和B组的张应力、应变能密度均表现出与死亡时间较好的相关性,是较好的推测死亡时间的生物力学参数。     

RNA指标在死后人体皮肤组织中稳定性研究

目的探讨多种RNA指标的表达水平在死后人体皮肤组织中的稳定性。方法收集死亡时间(PMI)明确的人体皮肤组织样本10例,提取总RNA,运用实时荧光定量PCR(qRT-PCR)技术检测ACTB、GAPDH、18S、miR-203、5S、1et-7a、RPS29、U6共计8个RNA指标的表达水平。geNorm软件评估各RNA指标表达水平的稳定性,挑选出稳定的内参指标并分析其表达水平与相关因素(年龄、性别、死因)的关系。结果人体皮肤组织中5S、U6和miR-203表达水平最为稳定,其平均表达量与年龄、性别、及死因无关(P0.05)。结论 5S、U6和miR-203可以作为qRT-PCR方法研究PMI的理想内参指标。     

Locard's Principle of Exchange,Dental Examination and Fragments of Skin

The transfer of materials between victim and perpetrator was first reported by Locard in the nineteenth century. While in recent years DNA testing has been very successful in matching biological material from crime scenes to perpetrators, the following cases demonstrate that other more time‐honored methods remain useful. Two cases of lethal assault are reported where the victims had bitten their assailants resulting in fragments of the perpetrators’ skin being wedged between their teeth which were discovered during post mortem oral examinations. As the fragments were able to be matched to injuries in the perpetrators, identification was established prior to confirmatory DNA testing. In case 1 a criminal conviction for manslaughter resulted, and in case 2 the identity of the assailant was confirmed. Examination of a properly exposed and illuminated oral cavity may provide useful evidence in assault cases. These cases represent an unusual dental variant of Locard's principle.     

Evidence of Premeditation in Skin Messages in Suicide

A 34‐year‐old man with manic‐depressive disorder was found dead sitting in a vehicle with a hose running from the exhaust pipe to the cabin. Numerous suicide notes were found inside his house. At autopsy, the decedent was wearing jeans and a long‐sleeved windcheater. Upon removal of his clothes, a series of messages were also found written on the legs and forearm. Death was due to carbon monoxide toxicity with a blood level of carboxyhemoglobin of 84%. Skin messages represent a rare form of suicide note that may suggest that a suicide has not been planned, as the decedent may have used the nearest surface to write on. This case demonstrates, however, that skin messages may be more organized, being written prior to dressing and setting up the fatal episode. They also may compliment other notes and messages.     

The Effect of Skin Debris on Gunshot Residue Sampling and Detection

These experiments were designed to determine whether skin debris (desquamated epithelial cells and apparent skin oils) affects gunshot residue (GSR) particle detection on the sticky tape lift samples prepared for scanning electron microscopy (SEM). A dabbing experiment showed that GSR particles accumulate not only on the adhesive surface of the sampler, but also on the epithelial cell surfaces. Samplers were loaded with target GSR followed by dabbing 30 times on the back of a hand. Backscatter electron images were taken at 20 kV and for some at 30 kV of the same areas. The samplers were then treated with a sodium/calcium hypochlorite solution (bleach) to remove skin debris and again imaged in the SEM. Comparison of these images shows more GSR particles will likely be revealed at 30 kV than 20 kV and more particles revealed by the bleach treatment in an automated SEM system.     

Relatively Permanent Pigmented or Vascular Skin Marks for Identification: A Pilot Reliability Study

In child sexual exploitation offenses, the collected evidence images often show the skin of nonfacial body parts of the criminals and victims. For identification in this scenario, “relatively permanent pigmented or vascular skin marks,” abbreviated as RPPVSM, were recently introduced as the basis for a novel biometric trait. This pilot study evaluated the interexaminer variability of RPPVSM identification. Four dermatology physicians were recruited to examine RPPVSM from 75 skin images collected from a total of 51 Caucasian and Asian subjects. The images were separated into 50 reference (“suspect”) images and 25 evaluation (“evidence”) images. The examiners were asked to perform identification by annotating RPPVSM in each of the 25 evaluation images and matching them with the reference images. The rate of misidentification was 0% while the mean rate at which examiners failed to find a match was 6%, indicating the potential of dermatology physicians performing the role of RPPVSM examiners.     

Touch DNA of Shed Skin Cells from the Deployed Airbag to Address Drunken Driving Crimes

In the criminal cases of driving under the influence （DUI）, DNA evidence can be collectedfrom the deployed airbag of the motor vehicle and submitted to the crime lab for touch DNA analysis.The evidence can be acquired when the skin cells are observed on the surface of the airbag in a trafficaccident. However, the low quantity or quality of the evidence collected from a crime scene preventsfurther identification analysis in many cases. In the current study, we reported a case of identifyingtouch DNA extraction from the shed skin cells from the deployed airbag of a motor vehicle. We man-aged to collect DNA evidence from the shed skin cells in an airbag using a proper approach of collec-tion and extraction. The 5.87 ng of extracted DNA was sufficient for genotyping and forensic identifica-tion, which helped to identify the driver of the car in collision with a pier in the street. In DUI casesand other traffic accidents, therefore, the amount of touch DNA extracted from the deployed airbag canbe sufficient for DNA marker genotyping and further analysis.