Forensic Science Review最新文献

Over the past few years, the phenomenon of new designer drugs has attracted much attention. Synthetic cannabinoids and cathinones are the two main classes of these drugs. Both are potent drugs of abuse, and several cases of severe toxicity and deaths are reported. The present work is based on a systematic review of studies that have assessed the market and prevalence of synthetic cannabinoids and cathinones, and integrates pharmacological, sociological, and epidemiological aspects of these two groups of emerging synthetic drugs. The review reflects that the Internet has made synthetic cannabinoids and cathinones widely available. Furthermore, aggressive and widespread marketing, as well as the low price level of these drugs, their juridical status and their lack of detection on standard drug tests may serve as major motivations for drug use. The number of prevalence studies is small and derived from a limited number of countries. In spite of the many methodological shortcomings, some conclusions may be cautiously drawn. Taken together, the results point toward higher prevalence of use for synthetic cathinones than for synthetic cannabinoids. In the general population, the prevalence of use of synthetic cathinones is reported to be around 4% compared to figures lower than 1% for synthetic cannabinoids. Among students, the prevalence varies from 1-20% for synthetic cathinones and 2-10% for synthetic cannabinoids. Among groups with high rates of drug use, the prevalence varies between 4% to more than 60% for synthetic cathinones and around 10% for synthetic cannabinoids.

Development of second- and third-generation DNA sequencing technologies have enabled an increasing number of applications in different areas such as molecular diagnostics, gene therapy, monitoring food and pharmaceutical products, biosecurity, and forensics. These technologies are based on different biochemical principles such as monitoring released pyrophosphate upon incorporation of a base (pyrosequencing), fluorescence detection subsequent to reversible incorporation of a fluorescently labeled terminator base, ligation based approach wherein fluorescence of cleaved nucleotide after ligation is measured, measuring the proton released after incorporation of a base (semiconductor-based sequencing), monitoring incorporation of a nucleotide by measuring the fluorescence of the fluorophore attached to the phosphate chain of the nucleotide, and by detecting the altered charge in a protein nanopore due to released nucleotide by exonuclease cleavage of a DNA strand. Analysis of multiple DNA fragments in parallel increases the depth of coverage while decreasing labor, cost, and time, highlighting some major advantages of deep-sequencing technologies. DNA sequencing has been routinely used in the forensic laboratories for mitochondrial DNA analysis. Fragment analysis, however, is the preferred method for Short Tandem Repeat genotyping due to the cumbersome and costly nature of fi rst-generation DNA sequencing methodologies. Deep-sequencing technologies have brought a new perspective to forensic DNA analysis. Studies include STR analysis to reveal hidden variation in the repeat regions, mtDNA sequencing, Single Nucleotide Polymorphism analysis, mixture resolution, and body fluid identification. Recent publications reveal that attempts are being made to expand the capability.

The analysis of dust allows inference of exposures to geographical areas, environments, activities, and processes. This activity of inferential source attribution is distinguished from that of comparative source attribution, where the focus is on the degree of correspondence between two sources in relation to other possible sources. Review of source attribution efforts in the forensic and broader scientific literature shows that most efforts are limited in one or more of four principal ways, which are classified as: (a) methods based on attribution by direct comparison; (b) methods based on closed-set item classification; (c) analysis using restricted methods and characteristics, and (d) requirement of a large sample size. These limitations provide the context for the requirements of more generalized inferential source attribution. Occurring much more rarely, and almost exclusively in the forensic literature, are individual source attribution case reports that have a microscopical, multidisciplinary perspective. Collectively these are an excellent illustration of potential and their common features demonstrate that (a) a diversity of laboratory expertise and methodology is required in order for source attribution to be successful; (b) different tools need to be applied in different cases, and (c) a process must be in place that allows a facile choice among this diversity of tools, in response to the particular investigative problem and the specifics of the samples that are available. Alternative collaborative mechanisms are considered and recommendations are made for related research and programmatic application.

For the past two decades, forensic DNA analysis has rapidly expanded in both utility and value to criminal investigations. As the number of crime scene and convict/arrestee samples has continued to grow, many forensic DNA laboratories find themselves struggling to test samples in a timely fashion. Agencies employ various methods for calculating their sample intake and processing capacity, yet database and casework sample backlogs continue to present a major challenge. One issue many forensic laboratories face is limited availability of resources for training new analysts. High-quality training enables analysts to effectively perform various aspects of DNA profiling, and as such, it is essential to ensuring consistent, high-quality results. This is well documented in the guidelines established in the FBI's Quality Assurance Standards for Forensic DNA Testing Laboratories in the United States as well as internationally by agencies like INTERPOL. A facility dedicated to training analysts on both theoretical and practical aspects of automated sample processing accelerates the establishment and expansion of high-throughput forensic DNA laboratories. The present article will discuss various aspects of training and agencies that provide such training programs.

Current practices for performing forensic mitochondrial DNA (mtDNA) sequence analysis, as employed in public and private laboratories across the United States, have changed remarkably little over the past 20 years. Alternative approaches have been developed and proposed, and new technologies have emerged, but the core methods have remained relatively unchanged. Once DNA has been recovered from biological material (for example, from older skeletal remains and hair shafts), segments of the mtDNA control region are amplified using a variety of approaches, dictated by the quality of the sample being tested. The amplified mtDNA products are subjected to Sanger-based sequencing and data interpretation is performed using one of many available software packages. These relatively simple methods, at least in retrospect, have remained robust, and have stood the test of time. However, alternative methods for mtDNA analysis remain viable options (for example, linear array assays and dHPLC), and should be revisited as the desire to streamline the testing process, interpret heteroplasmy, and deconvolute mixed mtDNA profiles intensifies. Therefore, it is important to periodically reassess the alternative methods available to the mtDNA practitioner, and to evaluate newer technologies being put forth by the scientific community, for example, next-generation sequencing. Although the basic mitochondrial DNA protocols and practices of public and private laboratories are similar, an overview of the current practices of forensic mtDNA analysis is provided, helping to frame the path forward.

Forensic DNA analysis using short tandem repeats (STRs) has become the cornerstone for human identification, kinship analysis, paternity testing, and other applications. However, it is a lengthy, laborious process that requires specialized training and numerous instruments, and it is one of the factors that has contributed to the formation and expansion of a casework backlog in the United States of samples awaiting DNA processing. Although robotic platforms and advances in instrumentation have improved the throughput of samples, there still exists a significant potential to enhance sample-processing capabilities. The application of microfluidic technology to STR analysis for human identification offers numerous advantages, such as a completely closed system, reduced sample and reagent consumption, and portability, as well as the potential to reduce the processing time required for biological samples to less than 2 h. Development of microfluidic platforms not only for forensic use, but clinical and diagnostic use as well, has exponentially increased since the early 1990s. For a microfluidic system to be generally accepted in forensic laboratories, there are several factors that must be taken into consideration and the data generated with these systems must meet or exceed the same guidelines and standards that are applicable for the conventional methods. This review covers the current state of forensic microfluidic platforms starting with microchips for the individual DNA-processing steps of extraction, amplification, and electrophoresis. For fully integrated devices, challenges that come with microfluidic platforms are covered, including circumventing issues with surface chemistry, monitoring flow control, and proper allele calling. Finally, implementation and future implications of a microfluidic rapid DNA system are discussed.