Authentication of evidence is always specific for each type of evidence and follows certain guidelines to judicial discretion. For one, Maps or Charts, it’s a general requirement that the original versions be used. In this regard, there may not be a need for originator of the material to confirm their authenticity as the mark ‘original’ may just suffice. In addition, sketches and diagrams generated by the police are as authentic as they are considered accurate within the judicial discretion. Anything that does not meet this threshold may easily be dismissed as hearsay. On the other hand, the use of photographs is generally broader as they as they meet the description of substantial and accurate depiction of the issue at hand. However, photographs that only support one party’s theory about the incident may be regarded as untrustworthy and therefore dismissed prematurely (Siemer, 1984).
Plaster casts and models are often considered the most admissible especially when they can be viewed in all the dimensions. More often than not, the construction material is immaterial as long as a three dimensional structure is obtainable. Furthermore, professional presentation or modifications that occur in models may be acceptable even if they are not precisely to scale. Conversely, microscopic enlargements are generally of limited application up to power twenty or less subjects to the criminal lab rules of the state involved (Koppenhaver, 1996).
Videotapes of confessions and depositions are often admitted in the criminal courts especially videotaping of drunk drivers although it is in most cases regarded as a real evidence rather than demonstrative evidence. However, the audio portions of the videotape must be discarded as it requires a separate authentication. Moreover, restructuring of images with the computer is generally accepted especially in forensic investigative procedures. However, they must conform to the projected possible outcomes as approximated by the computer. For example, figures relating to weights, lengths or surface measurements are fed into a computer algorithm to obtain simulations of an accident. The scientific demonstrations are of a greater significance before the court of law. Authentication of such evidence may involve performing the laboratory test in front of the jury so that they can draw their own independent conclusions and inferences. In such a case, the specialist carrying out the test is assumed to be sufficiently qualified and certainly aware of the expected results and that they must be consistent under similar conditions (Moenssens, et al., 1995).
Apart from demonstrative evidence satisfying the rules of authentication, it must go through several stages in the chain of custody. The first stage is the admissibility that involves showing the evidence to both parties and giving them adequate time to object before accepting it as a property of the court. This may at times technically incorporate pre-trial disclosure as required by the law on non-impeachment exhibits. After this stage, the court has a duty to determine the weight of the objections as concerns the demonstrative evidence. Finally, the judge will have the final say as to whether the demonstrative evidence can be held as reasonable grounds to sustain a course. This chain is always important to the success of a legal suit because it is the stage that determines whether the complainant may proceed to the Supreme Court or the Court of Appeal (Siemer, 1984).