Forensic toxicology is a science that deals with the application of toxicology in the situations that may involve medicological review and as a consequence the results may be subject to scrutiny in a court of law. The standard operating procedures or SOP describes all the routinely used analytical and administrative procedures. It basically serves as a document for the purpose of training. The field of forensics is such that it ay frequently demand deviation from the routine SOPs and may require modifications of the same. For an instance conditions that may involve accommodation of an unusual sample type or multiple, condition or unusual analytes. In toxicology, if any toxin is suspected, a specific analysis should be requested and the laboratories can simply just not check for poisoning. This calls for a complete description of epidemiological and clinical findings that may help in differentiating between infectious diseases and poisoining. The most common samples that are colled are the stomach contents, whole blood, kidney, liver, serum or urine. In some cases even the cerebral tiisues may also be collected for cholinesterase analysis. According to SOP, the tissue or fluid samples should be as fresh as possible and must be kept refrigerated. Freezing is essential for some analysis as it helps in preventing degradation of volatile chemicals. In rare circumstances a chemical preservative might also be required. The packaging and handling of the samples should be done very carefully. When there is a possibility of any legal action, the containers for shipment should be either sealed so as to enable detection of any form of tampering or be carried manually to the laboratory and the receipt of the same be recorded. There should be proper documentation of the chain of custody as well. When the suspected source of poison is feed or water, these samples, along with the samples of any feed tags should be sent along with the tissue samples (Merck manuals 2013).
All the incoming samples must be registered by the laboratory, Before signing the receipt, the samples are checked for their completeness, suitability and intactness for the testing purpose. If any sample is unlabelled or insufficiently marked, they are not processed and are sent back where appropriate. In any case the applicant must be informed and the details must be properly recorded in the laboratory files. The samples are assigned a laboratory internal code and ar clearly marked (using a barcode sometimes). The regulations of the Data Protection Act should be observed. In case of sample unsuitability or availability of less volume of sample for research or damaged sample, the laboratory immediately informs the applicant (Paul, L. et al. 2009).
It is important to identify the sample and the derivates produced by labeling the sample at every stage of analysis. After the completion of labeling process and analysis and the final report, the remains of the sample and the original containers should be kept or stored based on the administrative regulations. The samples other than blood samples can be stored atleast for six months while the blood samples can be stored for 2 years. Body fluids should be refrigerated as soon as received in the lab. If there is no possibility of extracting serum or plasma then a part of the full blood sample should be kept for deep freezing (-15oC) to prevent ageing of the sample matrix and any loss of the analytes. In case of the original blood withdrawal system that consist of the remaining blood, the measure of how much blood has been removed, should be accurately indicated with a mark. Urine samples or their aliquots should be deep frozen and stored after the receipt (Paul, L. et al. 2009).
The investigations can be divided into two major types: indicative and confirmatory (evidential) analysis. The former are the immune chemical test procedures that are simply based on the chromatographic techniques. The only drawback of indicative analysis was that the positive results of this test cannot be used as an evidence in court and should be confirmed by a second independent specific confirmatory method. The important point to be noted is that an immune chemical assay cannot be confirmed by second immunoassay. It is important for every laboratory to check if the cut off values of the immune chemical methods are properly calibrated and adequately chosen to differentiate between the positive and the negative results. The samples that are authentic give a positive result in the immune chemical pre testing procedure at the concentrations of the analyte in the limit that is required in the forensic toxicologic studies (Paul, L. et al. 2009).
After the processing of the samples is completed, the tedious job of compiling the results is next. According to the SOP guidelines, the forensic toxicology lab requires every procedure to be documented properly in order to maintain a co-ordinated record in relation to every sample or every case that is analysed. The records should contains enough details to allow identification of the factors that affect the uncertainity and also enable the scientists to repeat the whole test procedure, if required. This repetition of the experiement might be necessary in order to reproduce results as close as the original observations. Wherever needed, the results can be preserved in form of photos but photography is not allowed in every case. Sometimes electronic scanning is also a good option (eg. Thin layer chromatography results) (Swiss Confederation 2013). The SOP guidelines consider that digital images and photographs can provide importance evidence in criminal investigation and then prosecution. Some laboratories allow only the use of departmentally approved and issued digital cameral for official photography purpose. Right from the number of photographs, clarity of photographs, time of exposure, condition of the camera, time of issuing the camera to the type of photos that can be clicked, the assignment of responsibility of supervising the entire duration of photography coverage, every uideline or rule is mentioned in the Standard Operating Procedure manual. A special officer is allocated the task of managing and maintaining the confidentiality of the images that are clicked or taken and ensure safe transfer of the images into the laboratory database (Division of Criminal Justice 2013).
Division of Criminal Justice, 2013, A standard operating procedure for the use of digital images cameras by the First Responding Officer, viewed on 21st February 2015, www.nj.gov/oag/dcj/njpdresources/pdfs/digital_imaging%20_sop.pdf
Merck manuals, 2013, Overview of collection and submission of laboratory samples, viewed on 21st February 2015, https://www.merckmanuals.com/vet/clinical_pathology_and_procedures/collection_and_submission_of_laboratory_samples/overview_of_collection_and_submission_of_laboratory_samples.html#v3297560Paul, L. et al., 2009, Guideline for quality control in forensic toxicological analysis, GTFCh- Scietific Committee Quality Control.
Quest diagnostics, 2014, General guidelines, viewed on 21st February 2015, https://www.questdiagnostics.com/home/physicians/testing-services/specialists/hospitals-lab-staff/specimen-handling/general.html
Swiss Confederation, 2013, Guidelines for Accreditation of the Swiss Laboratories Performing Forensic Toxicological Analyses, Document No. 315 e.
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