Quality assurance testing of an explosives trace analysis laboratory--further improvements

The Forensic Explosives Laboratory (FEL) operates within the Defence Science and Technology Laboratory (DSTL) which is part of the UK Government Ministry of Defence (MOD). The FEL provides support and advice to the Home Office and UK police forces on matters relating to the criminal misuse of explosives. During 1989 the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could, if other precautions failed, result in the contamination of samples and controls. Designated areas within the laboratory are swabbed using cotton wool swabs moistened with ethanol water mixture, in equal amounts. The swabs are then extracted, cleaned up and analyzed using Gas Chromatographs with Thermal Energy Analyzer detectors. This paper follows on from a previous published paper describing the regime and summarizing subsequent results from approximately 6 years of tests. Lessons learned and improvements made over the period are also discussed. Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has demonstrated that in this environment the risk of forensic sample contamination, assuming all the relevant anti-contamination procedures have been followed, is so small that it is considered to be negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated.     

微量物证理化检验实验室认可工作的特点

文章结合我国微量物证检验工作的现状,对微量物证实验室认可工作的特点、难点以及认可中容易出现的问题进行了分析,在此基础上提出了具体的注意事项和建议。     

Visual detection of trace nitroaromatic explosive residue using photoluminescent metallole-containing polymers

The detection of trace explosives is important for forensic, military, and homeland security applications. Detection of widely used nitroaromatic explosives (trinitrotoluene [TNT], 2,4-dinitrotoluene [DNT], picric acid [PA]) was carried out using photoluminescent metallole-containing polymers. The method of detection is through the quenching of fluorescence of thin films of the polymer, prepared by spray coating organic solutions of the polymer, by the explosive analyte. Visual quenching of luminescence (lambda(em) approximately 400-510 nm) in the presence of the explosive is seen immediately upon illumination with near-UV light (lambda(ex)=360 nm). Detection limits were observed to be as low as 5 ng for TNT, 20 ng for DNT, and 5 ng for PA. In addition, experiments with normal production line explosives and their components show that this technology is also able to detect composition B, Pyrodex, and nitromethane. This method offers a convenient and sensitive method of detection of trace nitroaromatic explosive residue.     

Systematic analysis of explosive residues.

A scheme for systematic analysis of explosive residues is presented and demonstrated by test explosions using commercial, military, and homemade explosives. The significance of reaction product identification is demonstrated.     

Development of biological standards for the quality assurance of presumptive testing reagents

Forensic scientists periodically check working test reagents with knowns or standards to verify that the presumptive testing reagents are working properly. Oftentimes, this is done with a neat body fluid such as blood or saliva that is dried onto a swab and kept in a freezer. The problem with this practice is that a degrading test reagent, for example acid phosphatase testing reagent, may test positive on a neat standard but miss a weak semen stain from a case.To ensure that presumptive testing reagents are working properly, a series of “weak” standards have been developed for the testing of acid phosphatase, amylase, creatinine and hemoglobin. The preparation and use of these biological standards will be discussed.     

利用模具痕迹侦破爆炸案件

目的介绍模具痕迹检验方法,为侦察破案另辟蹊径。方法将提取的碎片拼合成形,推断为何物,收集同类产品进行比较,利用模具痕迹确定型号。结果根据型号找厂家,了解销售途径,扩大线索,寻找案件的突破口。结论模具痕迹检验是一种确定产品型号的好方法。     

Quality assurance review of death certificates: a pilot study

BACKGROUND: Although quality assurance programs for medical examiners are required by the National Association of Medical Examiners' Inspection and Accreditation Checklist, quality assurance programs specifically targeting death certificate completion have not been addressed. The Fulton County Medical Examiner, Atlanta, GA, has implemented a pilot quality assurance program for death certificate information, and this report contains information about 1 year's experience with the program. METHODS: All death certificates are reviewed by the case medical examiner(s) and chief medical examiner prior to their release to funeral homes. Death certificates with errors are retained for quality assurance and review purposes, and needed corrections are made before death certificates are released. During a 1-year period, death certificates with errors were collected and then reviewed and tabulated by type of error. RESULTS: Between May 26, 2003, and May 25, 2004, the Fulton County Medical Examiner certified 1267 deaths. Of these, 47 (4%) were found to contain errors that were corrected and an additional 52 (4%) had been amended for various reasons. The most common errors were misspellings in causes of death or poor or incomplete wording in injury-related information. Forty-seven percent of errors involved omitted, incomplete, or incorrect information that was potentially significant. The most common reason for amended certificates was unexpected detection of acute intoxications among people with significant cardiovascular disease. CONCLUSIONS: Quality assurance review of death certificates can assist in preventing the release of death certificates with incomplete, erroneous, or omitted information and may also be useful as an educational forum regarding completion of the death certificate.     

Effectiveness of contamination prevention procedures in a trace explosives laboratory.

The effectiveness of a number of the explosives contamination prevention controls that are adopted within the Forensic Explosives Laboratory (FEL) principal trace laboratory has been scrutinised. Within the trace laboratory, rigorous procedures for processing forensic swab samples for traces of organic explosives are routinely adopted by forensic scientists. In order to demonstrate the effectiveness of these procedures, and the principle of separating the sample from the laboratory and the forensic scientist, explosives-free swab samples and appropriate controls have been processed, in accordance with trace laboratory procedures, in several explosives contaminated environments. In all cases, no explosives were detected in the post-processing samples, demonstrating that the contamination prevention procedures are effective, robust and fit-for-purpose.     

Quality assurance in nuclear medicine facilities; availability of final recommendations--FDA. Notice

The Food and Drug Administration (FDA) is announcing the availability of final recommendations prepared by its Center for Devices and Radiological Health (CDRH) on quality assurance programs in nuclear medicine facilities. The final recommendations include the agency's rationale for the recommendations as well as references that can be used as well as references that can be used as guides in conducting quality control monitoring. These final recommendations are available as a technical report in CDRH's radiation recommendations series. They are intended to encourage and promote the development of voluntary quality assurance programs in nuclear medicine facilities.     

Quality assurance and hospital structure: how the physician-hospital relationship affects quality measures

Mr. Spaeth writes about the relationship between hospital administration and the physician, and how that relationship affects the quality of medical care delivered to the patient. The article focuses on the differences between the employment structure in an academic teaching hospital, and the open, independent contractor medical staff typical of a traditionally smaller community hospitals. The individual traits and nuances of these structures and how they can be distinguished from one another create dynamic differences in the approach for quality care. Peer review, credentialing, and management of adverse outcomes are just a few of the ways in which hospitals continue to strive to provide higher quality care, but the way these methods are implemented and performed in different hospital structures are dramatically different, yielding distinct results. Mr. Spaeth argues that the challenges faced by community hospitals in their effort to provide higher quality care and eliminate medical error are exacerbated because of their unique structure and the particular relationship physicians share with the hospital and its administration.     

Evaluation of amylase testing as a tool for saliva screening of crime scene trace swabs

Amylase testing has been used as a presumptive test for crime scene saliva for over three decades, mainly to locate saliva stains on surfaces. We have developed a saliva screening application for crime scene trace swabs, utilising an amylase sensitive paper (Phadebas^® Forensic Press test). Positive results were obtained for all tested dried saliva stains (0.5–32 μL) with high or intermediate amylase activity (840 and 290 kU/L). Results were typically obtained within 5 min, and all samples that produced DNA profiles were positive. However, salivary amylase activities, as well as DNA concentrations, vary significantly between individuals. We show that there is no correlation between amylase activity and amount of DNA in fresh saliva. Even so, a positive amylase result indicates presence of saliva, and thereby presence of DNA. Amylase testing may be useful for screening in investigations where the number of DNA analyses is limited due to cost, e.g., in volume crime.     

Hair analysis for cocaine: Factors in laboratory contamination studies and their relevance to proficiency sample preparation and hair testing practices

Hair samples were contaminated by rubbing with cocaine (COC) followed by sweat application, multiple shampoo treatments and storage. The samples were then washed with isopropanol for 15 min, followed by sequential aqueous washes totaling 3.5 h. The amount of drug in the last wash was used to calculate a wash criterion to determine whether samples were positive due to use or contamination. Analyses of cocaine and metabolites were done by LC/MS/MS. These procedures were applied to samples produced by a U.S. government-sponsored cooperative study, in which this laboratory participated, and to samples in a parallel in-house study. All contaminated samples in both studies were correctly identified as contaminated by cutoff, benzoylecgonine (BE) presence, BE ratio, and/or the wash criterion. A method for determining hair porosity was applied to samples in both studies, and porosity characteristics of hair are discussed as they relate to experimental and real-world contamination of hair, preparation of proficiency survey samples, and analysis of unknown hair samples.     

Hair analysis for cocaine: factors in laboratory contamination studies and their relevance to proficiency sample preparation and hair testing practices

Since the introduction in 2001 of a urine-based detection method for recombinant erythropoietin (rHuEPO), transfusion-doping practices have regained interest. To address this problem, an efficient antidoping test designed to obtain direct proof of allogeneic blood transfusion was developed and validated. This test, based on flow cytometry analysis of red blood cell (RBCs) phenotypes, was used to determine the absence or the presence of numerous RBCs populations in a blood sample. A such, it may constitute a direct proof of an abnormal blood population resulting from homologous transfusion. Single-blind and single-site studies were carried out to validate this method as a forensic quality standard analysis and to allow objective interpretation of real cases. The analysis of 140 blood samples containing different percentages (0-5%) of a minor RBCs population were carried on by four independent analysts. Robustness, sensitivity, specificity, precision and stability were assessed. ISO-accredited controls samples were used to demonstrate that the method was robust, stable and precise. No false positive results were observed, resulting in a 100% specificity of the method. Most samples containing a 1.5% minor RBCs population were unambiguously detected, yielding a 78.1% sensitivity. These samples mimicked blood collected from an athlete 3 months after a homologous blood transfusion event where 10% of the total RBCs present in the recipient originated in the donor. The observed false negative results could be explained by differences in antigen expression between the donor and the recipient. False negatives were more numerous with smaller minor RBCs populations. The method described here fulfils the ISO-17025 accreditation and validation requirements. The controls and the methodology are solid enough to determine with certainty whether a sample contains one or more RBCs populations. This variable is currently the best indicator for homologous blood transfusion doping.     

改良IPEP法用于痕量DNA检测的实验研究

目的探讨改良扩增前引物延伸(IPEP)法对痕量DNA样本STR检测分型的效果。方法用改良IPEP法对痕量样品DNA进行全基因组扩增(WGA),扩增产物用实时荧光定量PCR技术定量、用AmpFLSTR~ Indentifiler~试剂盒作基因型检测。结果该方法可增加模板DNA约200~1100倍。基因组DNA不低于0.025ng时,可获得15个STR基因座和Amelogenin性别基因座的分型结果。基因组DNA0.01~0.025ng时,可获得9个以上基因座的分型结果。结论改良IPEP法可有效提高痕量DNA样本STR分型检验的灵敏度,有较好的实用价值。     

Headspace concentrations of explosive vapors in containers designed for canine testing and training: theory, experiment, and canine trials

It is a common misconception that the amount of explosive is the chief contributor to the quantity of vapor that is available to trained canines. In fact, this quantity (known as odor availability) depends not only on the amount of explosive material, but also the container volume, explosive vapor pressure and temperature. In order to better understand odor availability, headspace experiments were conducted and the results were compared to theory. The vapor-phase concentrations of three liquid explosives (nitromethane, nitroethane and nitropropane) were predicted using the Ideal Gas Law for containers of various volumes that are in use for canine testing. These predictions were verified through experiments that varied the amount of sample, the container size, and the temperature. These results demonstrated that the amount of sample that is needed to saturate different sized containers is small, predictable and agrees well with theory. In general, and as expected, once the headspace of a container is saturated, any subsequent increase in sample volume will not result in the release of more vapors. The ability of canines to recognize and alert to differing amounts of nitromethane has also been studied. In particular, it was found that the response of trained canines is independent of the amount of nitromethane present, provided it is a sufficient quantity to saturate the container in which it is held.