The use of expert witnesses has grown to become an integral aspect of the U.S. litigation system. Expert witnessing involves the use of science in the courtroom to advise the trier of fact, i.e., both the juries and judges, on scientific and technical issues surpassing their general knowledge and understanding. Properly qualified and admissible expert testimony is a powerful piece of evidence. This is because it has the capability of identifying a potential suspect while excluding others.
Before appearing in court, the witness has to draft a report. An expert report contains the expert’s qualification, relevant experience, a statement of all the substance of facts, details about who carried out the examination and the tests used, and a summary of conclusions from the test results.
Moreover, not all expert testimony is admissible in court. Several standards are governing the admissibility of expert evidence in court. They comprise the Frye standard, Rule 207, and the Daubert standard. However, the commonly used standard in criminal litigation is the Daubert standard. The expert testimony will consist of the evidence collected and examined. It is essential to mention the standard lab procedures used to examine the evidence. Furthermore, it contains a conclusion such as identification, exclusion, and inconclusive to express opinions as to whether an individual or object is the source of unknown evidence collected from a scene. Source identification is regarded as the phenomenon when both materials come from the same source. This is vice versa for source exclusion. However, inconclusive is the phenomenon where an examiner is unable to identify or two objects as originating from the same source. Expert witnesses may also use probability or likelihood ratios to express their opinion.