Chain of evidence

The term definitive method is applied to an analytical or measurement method that has a valid and well described theoretical foundation, is based on sound theoretical principles ( first principles ), and has been experimentally demonstrated to have negligible systematic errors and a high level of precision. While a technique may be conceptually definitive, a complete method based on such a technique must be properly applied and must be demonstrated to deserve such a status for each individual application. A definitive method is one in which all major significant parameters have been related by a direct chain of evidence to the base or derived SI units. The property in question is either directly measured in terms of base units of... 

Forensic analysis is usually required for the collection of data in the course of determining whether legislation has been infringed. The customer requires that, above all, there is an unbroken chain of evidence from the time the samples were taken to the presentation of evidence in courts of law. In the laboratory this will include documentation and authorization for sample receipt, sample transfer, sub-sampling, laboratory notebooks, analytical procedures, calculations and observations, witness statements and sample disposal. All of these aspects can be called as evidence in court. 

Ades, A. 2003. A Chain of Evidence with Mixed Comparisons Models for Multiparameter Syntheses and Consistency of Evidence. Statistics in Medicine 22 2995-3016. 

This automated system should also permit examiners to transmit the information contained in the rifling markings on a bullet or the impressions of the breech of a firearm that appear on the head of a discharged shell to examiners in other localities, rapidly and accurately, without the worry of preserving the continuity of the chain of evidence that becomes our primary concern when transporting evidence and firearms. 

In real off-site sample analysis, the designated laboratory s report must stand up to international scrutiny and must be legally and scientifically defensible. Within the report, an unbroken chain of evidence must therefore be established linking each sample aliquot to each chemical identified by a defined method of analysis. A way of establishing such a clear link is by naming the aliquot in the sample preparation flowchart, and subsequently using this aliquot name either as a file name or as a sample name in the instrumental analysis to be employed. 

The location of the enzymes of anunonia assimilation in organelles known to carry out the pathway is a necessary link in the chain of evidence but again it is all too easy to obtain false positive evidence or to produce negative results. Unfortunately there are very many poor papers in the literature on enzyme localization in plant tissues and there is a need for careful critical appraisal of such results. Finally it must be emphasized that because an enzyme is present it does not mean that it is functional in any given pathway or that it works in the direction it is usually assayed. Despite this, one of the most frequently heard (if not written) arguments in favor of a role for GDH in assimilation is that because the enzyme is there and can be readily assayed in the amination reaction, (albeit using strong concentrations of ammonia) that must be its function. ... 

An important feature of this approach is that only the standards that realize the unit of length require a documentary chain of evidence that links to the definition of the meter. In a typical dimensional measurement, there are many influence quantities that contribute to the uncertainty associated with the end result, such as workpiece temperature and thermal expansion coefficient. If it were required that all such influence quantities themselves be metrologically traceable, then since each of the quantities depends on other quantities and so on, such a requirement would lead to an infinite regress. 

Case study tactics Use of multiple sources of evidence, establish chain of evidence, have key informants review draft case study report. 

For the results to be valid, it is essential that not only the items (crime or comparison samples) must be collected in a controlled, reproducible fashion, but also following an admissible legal procedure that varies from country to country (e.g., chain of evidence in common law seals in other formal legal systems). 

Scepticism persisted, nonetheless. It thrived upon several different issues and apparent anomalies. The first was the chain of evidence. 

Yin 1994, p. 34). The first is the use of multiple sources of evidence. The second tactic is to establish a chain of evidence. The third way is to have the draft case study report reviewed by key informants (Yin 1994, pp. 34—35). 

Kipping reported that Compound B (decaphenylcyclopentasilane) reacted with bromine to give a mixture of products. These were subsequently hydrolyzed and a cyclic dioxide was isolated. This compound has more recently been shown to be octaphenyl-l,4-dioxacyclohexasilane. It has been found that careful addition of an equivalent amount of bromine to decaphenylcyclopentasilane (6) in benzene results in a high yield of 1,5-dibromodecaphenylpentasilane (21). > This dibromo compound was one of the important links in the chain of evidence leading to the correct structure of decaphenylcyclopentasilane. 

Any break in the chain of evidence documentation may compromise the evidential value of the sample. 

Fig, 4.4 Chain of evidence form. From Health Protection Agency document CBRN Incidents Clinical Management and Health Protection (available online at www.hpa.org.uk), and used with permission. 

Chain of evidence forms should be completed if necessary... 

Toxicological testing is vital in order to determine or confirm which chemical agent is implicated so that treatment and further resources can be organised effectively. For forensic reasons, the chain of evidence must be maintained at every stage. 

In cases of suspected intentional chemical release it is vital that all casualties personal effects, such as clothing, and samples are kept appropriately packaged and documented to ensure that the chain of evidence is maintained. This is especially relevant where samples may pass between several different departments or laboratories. Every movement of a sample should be documented. The consultant in... 

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