Request, receipt and storage
It is the responsibility of the laboratory to advise its clients (e.g. coroner, medical examiner, lawyers, pathologist) what types and amounts of specimens are required for postmortem toxicology testing, and what preservative, if any, should be used. At least one tube of whole blood preserved with 1% sodium fluoride should be provided, to be reserved for testing for ethanol and drugs such as cocaine. Stomach contents and most tissues are usually providedunpre served. A recommended list of specimens is given in Table 7.1 together with an indication of volumes required for analysis. The laboratory should provide guidelines on specimen collection and storage as well as a requisition, to be completed by the submitter, which should be sent with the specimens to the laboratory. The requisition serves five primary purposes:
• it identifies the deceased and gives appropriate demographic information and case history (e.g. circumstances of death, relevant medical history, autopsy findings)
• it identifies the specific specimens and exhibits submitted
• it provides space to identify the testing required
• it identifies the submitter and serves as a chain-of-custody document
• it provides directions and information for packaging and transport of the specimens.
Each specimen must be labelled uniquely to identify the deceased from which the specimen was obtained (i.e. name or case number), and the specimen type. Figure 7.1 gives an example of a requisition for postmortem specimen analysis. The layout, terminology and exact content of such requisitions will vary depending on the particular jurisdiction but the information requested is universally applicable. The extent of information requested depends on the jurisdiction in which the toxicologist is working. Where most samples are transferred internally within a medical examiner facility, department of forensic medicine or forensic toxicology laboratory, a less-detailed case history or autopsy summary may be required if it can be readily obtained later. Upon receipt in the laboratory, the specimens submitted must be checked against the information given on the requisition. Where there is more than one specimen of the same type, each container should be labelled uniquely (e.g. A, B, C, . . .), since, with the exceptions of urine, vitreous humour and bile, postmortem specimens are not homogeneous and different containers of the same specimen type (e.g. blood) can sometimes have different drug concentrations. Receipt of the specimens must be recorded, on paper or electronically. That log should include:
• appropriate demographic information
• an adequate description of the specimen and its site of sampling (e.g. femoral blood)
• the approximate volume or mass
• the type of container (e.g. grey-stoppered tube)
• any abnormal appearance of the specimen (e.g. decomposed, heat denatured, bloody urine, and so on).
If preservative has been added to the specimen, as is often the case for blood samples, this should be noted in the log against the appropriate sample. All laboratories that undertake postmortem toxicology should document the chain of custody. At a minimum, the laboratory should document what was received, from whom, by what means (by hand, courier, mail) and when. Storage of the specimens and exhibits should be secure, and access to specimens and case files should be limited to authorised laboratory personnel. Blood and other tissue specimens should be stored under refrigerated conditions between receipt at the laboratory and analysis. A record should be kept of each occasion the specimen is opened to remove an aliquot. The date when specimens are discarded or returned to the submitter should also be recorded. The length of retention of tissues by the laboratory may be a set period of time (e.g. 3 to 12 months agreed with the client), or the time required to complete any legal proceedings. In the UK there are strict rules on sampling and storage of human tissues and this extends to postmortem samples. Post mortem toxicological analysis is normally requested via the coroner and all samples are officially under his or her jurisdiction. Permis sion must be obtained from the coroner for disposal of samples.
