Explain the concept of chain of evidence as it applies to the process of investigating a crime.
Chain of evidence, also known as chain of custody, deals with the handling of evidence that is recovered from a crime scene (Wigmore 2007). This rule of evidence requires that from the exact moment a piece of evidence (circumstantial or otherwise) is recovered the transfer of the possession of the evidence from person to person must be documented (Wigmore 2007). It must also be clearly shown that the evidence is the same one that was recovered at the scene of the crime and that there was no other way that such evidence could have been tampered with by other people. In this light, it is therefore important that under the chain of evidence the number of people who come into possession of the evidence or the number of transfers must be kept to a minimum (Wigmore 2007).
A perfect example of how the concept of Chain of evidence works can be best shown by the following situation. In a certain crime scene, there is a gun that is found lying around close to the dead body. The police officer who finds such weapon then carefully gets the gun and places it in an evidence bag. This same bag containing the gun is then handed over to the forensics expert or crime scene investigator who processes the same. Once it has been tagged and documented, the same gun will then be given to the prosecutor who will present such evidence (if relevant) in court. This is the basic process of the chain of evidence as applied in the process of investigating a crime.
It must also be remembered, however, that the Chain of Evidence does not only apply to this kind of scenario but can also be applied to others as well. One perfect example of this would be when the chain of evidence is used in certain chemical sampling scenarios. The relevance of chain of evidence in this would be that the integrity of the sample must be shown by proving that there was proper documentation in the control, transfer and analysis of the chemical samples.
It is very important to maintain the integrity of evidence because evidence can be rendered inadmissible in court if it cannot be shown that there was a proper chain of evidence. In the scenario involving the gun, which was earlier discussed, such piece of evidence can be disallowed in court if it is shown that the evidence may have been tampered with or if there was a gap in the chain of evidence.
The reason behind this is that it is essential to prove that this was the very same gun that was recovered from the scene of the crime. The law on evidence and procedural law require that for an object to be introduced in court as evidence it must be shown in court and formally offered as evidence (Wigmore 2007). Since this is a strict procedural requirement under the law, the integrity of the evidence that is presented must be shown. Mere police statements or testimonies that speak of the existence of such weapon will not suffice (Wigmore 2007). It is important that the very same weapon be produced in court and hence the importance of maintaining its integrity by following a strict chain of evidence (Wigmore 2007).
In order to follow this chain of evidence, there are certain very strict guidelines that have been lain down by state law (Wigmore 2007). Under the law, only an authorized person is allowed to have possession of the evidence in question. Such physical custody must also be clearly documented. This is then required to be deposited to the evidence clerk or other competent personnel (Wigmore 2007). It must be remembered that at every transfer there must be a clear documentation of where the piece of evidence was obtained from, whose possession it was with prior to the transfer and the identity of the person to whom the same will be given (Wigmore 2007). Other documentation requirements may include the conditions under which the object was gathered, the duration of custody, security conditions, and the manner of transfer to other personnel (Wigmore 2007).
Wigmore (2007) Wigmore on Evidence Set, Fourth Edition Aspen Publishers United States ISBN: 0316939706