.
iii) Contamination.
It is frequent that individuals who are involved in the collection and handling of evidence are requested to testify in court, therefore the quality of their work must be high, "the evidence must be kept free from contamination"[Nic99].
According to Beaufort-Moore [Bea09], contamination occurs when something is added to the sample, accidentally or deliberately. This can happen, for example, when an officer sneezes over material that potentially bears DNA; the officer's DNA can then contaminate the evidence, making it inadmissible in court [Coy10]. .
Contamination of evidence can occur due to weather conditions, poor scene control, poor collection techniques, so on and so forth. It can occur at several stages, including at the crime scene, during the collection or the transport of evidence, on submission of evidence, during analysis, on final storage of the exhibits [Dea05]. To avoid contamination, investigators and laboratory personnel should use the appropriate procedures and wear protective clothes[Dut11]. .
A notorious example of contamination is the case of Adam Scott, who was charged with rape after a plastic tray containing a sample of his DNA was re-used in the analysis of a swab from the victim. The result of that test was the only evidence linked him to the crime[Her12]. However, the mistake was discovered and the accused has been released a few months later.
Legal Governance of Crime Scene Examination.
i) The Crime Scene Examiner in a Court of Law.
There are no clear criteria for the designation of someone as an expert, although there are a number of bodies that represent expert witnesses or maintain registers or membership lists [Bro72]. The Council for Registration of Forensic Practitioners used to be the regulatory body for CSIs, it assessed and accredited the competence of individuals in most forensic science disciplines to give expert evidence in court, but it was disbanded in 2009 [Pep05].