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.     

Quality assurance testing of an explosives trace analysis laboratory — Further improvements to include peroxide explosives

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 analysed using Gas Chromatography with Thermal Energy Analyser detectors or Liquid Chromatography with triple quadrupole Mass Spectrometry. This paper follows on from two previous published papers which described the regime and summarised results from approximately 14 years of tests. This paper presents results from the subsequent 7 years setting them within the context of previous results. It also discusses further improvements made to the systems and procedures and the inclusion of quality assurance sampling for the peroxide explosives TATP and HMTD. 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.     

Evaluation of canine training aids containment for homemade explosive and components by headspace analysis and canine testing

While canines are most commonly trained to detect traditional explosives, such as nitroaromatics and smokeless powders, homemade explosives (HMEs), such as fuel–oxidizer mixtures, are arguably a greater threat. As such, it is imperative that canines are sufficiently trained in the detection of such HMEs. The training aid delivery device (TADD) is a primary containment device that has been used to house HMEs and HME components for canine detection training purposes. This research assesses the odor release from HME components, ammonium nitrate (AN), urea nitrate (UN), and potassium chlorate (PC), housed in TADDs. Canine odor recognition tests (ORTs) were used with analytical data to determine the detectability of TADDs containing AN, UN, or PC. Headspace analysis by gas chromatography/mass spectrometry (GC/MS) with solid-phase microextraction (SPME) or online cryotrapping were used to measure ammonia or chlorine, as well as other unwanted odorants, emanating from bulk AN, UN, and PC in TADDs over 28 weeks. The analytical data showed variation in the amount of ammonia and chlorine over time, with ammonia from AN and UN decreasing slowly over time and the abundance of chlorine from PC TADDs dependent on the frequency of exposure to ambient air. Even with these variations in odor abundance, canines previously trained to detect bulk explosive HME components were able to detect all three targets in glass and plastic TADDs for at least 18 months after loading. Detection proficiency ranged from 64% to 100% and was not found to be dependent on either age of material.     

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.     

Linking ammonium nitrate-aluminum (AN-AL) post-blast residues to pre-blast explosive materials using isotope ratio and trace elemental analysis for source attribution

Forensic science practitioners are often called upon to attribute crimes using trace evidence, such as explosive remnants, with the ultimate goal of associating a crime with a suspect or suspects in order to prevent further attacks. The explosive charge is an attractive component for attribution in crimes involving explosives as there are limited pathways for acquisition. However, there is currently no capability to link an explosive charge to its source via post-blast trace residues using isotope ratios or trace elements. Here, we sought to determine if pre-blast attribution signatures are preserved after detonation and can be subsequently recovered and detected. A field study was conducted to recover samples of post-blast explosives from controlled detonations of ammonium nitrate-aluminum (AN-Al), which were then analyzed via isotope ratio mass spectrometry (IRMS) and inductively coupled plasma-mass spectrometry (ICP-MS) for quantitation and profiling of isotopes ratio and trace element signatures, respectively. Oxygen and nitrogen isotope ratios from AN-Al yielded some of the most promising results with considerable overlap within one standard deviation of the reference between the spreads of pre- and post-blast data. Trace element results from AN-Al support the findings in the isotope ratio data, with 26 elements detected in both pre- and post-blast samples, and several elements including B, Cd, Cr, Ni, Sn, V, and Zn showing considerable overlap. These preliminary results provide a proof-of-concept for the development of forensic examinations that can attribute signatures from post-blast debris to signatures in pre-blast explosive materials for use in future investigations.     

The laboratory testing of evidential breath-testing (EBT) machines

Six types of evidential breath testing (EBT) machines were tested in a laboratory. The testing experiments are classified into three paragraphs: analytical performance, sampling and operating conditions. In order to characterize the analytical performance a set of parameters (repeatability, reproducibility, linearity, accuracy, specificity) was established. The results were, in general, good, although an underestimation of the actual vapour concentration was observed. Different types of EBT machines showed significant differences measuring the same vapour.     

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.     

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.