Elucidation of the effect of heat exposure on hair colored by permanent and semipermanent colorants using surface-enhanced Raman spectroscopy

Confirmatory identification of hair colorants can be used to establish a connection between a suspect and the crime science or demonstrate the absence of such connections. A growing body of evidence shows that surface-enhanced Raman spectroscopy (SERS) could be a confirmatory, minimally destructive, and fully noninvasive analysis of hair colorants. In SERS, a signal that provide the information about the chemical structure of both permanent and semipermanent dyes present on hair is enhanced by a million-fold using noble metal nanostructures. However, it is unclear whether the information of hair colorants can be revealed if hair was contaminated or exposed to harsh environments such as sunlight and heat. In this work, we determine the effect of a short- and long-term heat exposure on SERS-based analysis of hair colored with blue and red permanent and semipermanent dyes. We found that short and especially long-term heat exposure at 220°C could alter chemical structure, and consequently SERS spectra, of permanent and semipermanent colorants. This thermal degradation of permanent dyes complicates their direct identification using SERS. We also found that partial least squares discriminant analysis can be used to overcome this issue allowing for highly accurate identification of both permanent and semipermanent dyes on colored hair that was exposed to 220°C for 6–12 min. These results show that heat exposure of colored hair should be strongly considered upon their SERS-based examination to avoid both false positive or false negative identification of chemical dyes.     

Latent Fingerprint Development on Thermal Paper Using Traditional Ninhydrin and 1,2‐indanedione

Thermal paper poses a significant challenge to latent print development as it tends to change color when traditional fingerprint development formulations are applied to it. In this study, the optimal components of ninhydrin, 1,2‐indanedione, 1,8‐diazafluoren‐9‐one (DFO), and 5‐methylthioninhydrin (5‐MTN) for yielding clear fingerprints on thermal paper were determined by systematically adjusting the relative amounts of the reagents, polar solvents, and the nonpolar diluent petroleum ether, followed by validation on text‐printed thermal paper. Specifically, 3.0% ethyl acetate as the polar solvent in petroleum ether was found to be the optimal combination; the optimal dilution ratios of ninhydrin, DFO, and 5‐MTN original solutions with petroleum ether were 1 to 2, 11, and 7, respectively. The optimal concentration of 1,2‐indanedione in petroleum ether was 0.125 g/L, with a string of 0.5% ethyl acetate in petroleum ether.     

Projectile Wound to Head from Modified Electronic Cigarette Explosion

One of the dangers of a rapidly growing technology industry is the risk involved in being intimately close to lithium-ion batteries. When exposed to improper conditions, lithium-ion batteries in a variety of devices have been reported to ignite and, in some cases, explode. With the rise of electronic cigarette use and modifications, the lithium-ion batteries in these devices are subject to a higher risk of malfunction. This is a retrograde analysis of a 38-year-old man who experienced fatal penetrating head trauma while using a modified electronic cigarette device. The findings suggest that the trauma from the explosion was caused by the thermal runaway of the lithium-ion battery in the modified e-cigarette.     

Modeling Temperature Variations Using Monte Carlo Simulation: Implications for Estimation of the Postmortem Interval Based on Insect Development Times*†

The association between insect development and temperature is well established. Thermal summation using accumulated degree-day measures is commonly used. However, the time at which evidence is collected is important in these estimates. The aim of this study was to provide a simulated model of the effect of temperatures on six dipteran species commonly associated with cadavers, from the death scene to the refrigerator, and finally at the time of autopsy. Temperatures measurements were sampled over a 16-month period from the external environment (external to the mortuary), within the mortuary refrigerator, and within the mortuary autopsy suite. Monte Carlo simulation using accumulated degree-days (ADD) was used to estimate the variations based on the mean and standard deviation of the temperature measurements. It was found that there was a negative correlation between the base temperature of the fly species (lowest temperature at which the flies will survive) and developmental likelihood. Species with high base temperatures (Chrysomya albiceps, Chrysomya chloropyga, and Musca domestica) were less likely to continue development in refrigerators than species with lower base temperatures (Lucilia sericata and Piophila casei). The findings of this study highlight the importance of recording temperature measurements and the period of refrigeration on PMI estimation especially when continued development occurs in spite of a period of cooling of the insect evidence.     

The Effect of Time and Temperature on the Persistence and Quality of Latent Fingerprints Recovered from 60-Watt Incandescent Light Bulbs

To understand how time and temperature could affect latent fingerprints, wooden pallets were used to construct five units that each housed ten 60-watt incandescent light bulbs. Fingerprints were deposited on the top, middle, and base of the globes. The bulbs were powered on (except the control bulb in each unit) for 18, 48, 72, 120, 168, 336, 504, and 672 h. Fingerprints recovered from the bulbs by tape lift after black powder processing were given a quality score. A thermal imaging camera determined temperatures on three areas of the bulbs. Fingerprints on the top of the globe (156.3°C) had the lowest quality score, and fingerprints on the middle of the globe (112.6°C) had the highest quality score. The mean quality scores of the three temperature classes were within one standard deviation of one another, meaning there is no way to estimate fingerprint age based on its quality after heat exposure.     

谈现场急救中的冷处理

文章对冷处理方法的适用范围、冷处理的作用机制、冷处理的操作方法及体会进行了阐述。冷处理方法在运动损伤、急性软组织挫伤、烧烫伤、中暑及某些疾病发作等情况下可能用到,可以根据不同的伤病情和现场的条件灵活地采取有效的方法实施自救和互救。     

Fast PCR amplification of AmpFlSTR Identifiler

To increase throughput for DNA typing, we examined fast PCR cycling using AmpFlSTR Identifiler by three methods. In this study, we reduced PCR running times by 1/3 to 2/3 (approximately 1-2 h). This means DNA typing, including PCR reactions, can be completed within a timeframe ranging from 90 min to 2 h and 30 min.     

热敏纸表面上汗潜指纹的显现

茚三酮溶液显现法是显现普通纸表面汗潜指纹的常用方法。但是由于热敏纸表面涂有热敏涂料,使得上述方法在该客体表面汗潜指纹的显现中难以奏效。不过,在此方法基础上改良发展而来的1,2茚二酮法、二甲基氨基肉桂醛法、过量丙酮冲洗法、半醇酮茚显现法等4种方法能取得较好效果。     

深圳市“11．19”重大火灾事故的法医学鉴定

火灾事故的法医学鉴定是司法鉴定实践中的一个重要课题。１９９３年１１月１９日深圳致丽玩具厂发生重大火灾事故，烧死８７人，烧伤５１人。本文对事故中受难者的死亡原因及个人识方法别进行了分析。并对处理类似重大事故的法医学鉴定程序进行了探讨。     

应用扫描电镜能谱仪检测电击伤皮肤表面的金属元素——附一例案例报告

作者采用已知化学组成的导体对家兔进行触电试验。取受损部位的皮肤作常规处理,用带能谱的扫描电镜作金属离子测定,仪器型号为 JXA-840-LinK-860。对检出的金属元素,进行了定性和半定量分析,并观察了元素的分布。作者在一例人体电击伤皮肤活检标本上检出铁元素,而对照皮肤则无,从而认定是含铁的导体与皮肤接触。电击伤与热烫伤的超微结构变化能区别。