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How to Admit Expert Witness Testimony in Criminal Cases

It is critical that the testimony of an expert witness is within the evidence, statements and other testimony in a criminal case so that the defendant faces a stronger chance of conviction or a not guilty verdict. To provide the defense party with a greater chance of success, the expert witness may give the case the much-needed details that clear up confusion.

Admitting testimony to a criminal case is complex and difficult depending on which side the expert witness will take. When the prosecution hires these professionals, it is less likely that they will face disqualification. However, the defendant’s party usually has a much more complicated process. The credentials and methods used by the witness are important. If the expert cannot ensure that his or her processes are both relevant and reliable, he or she may not have admissible testimony. In federal cases, these factors become more extreme. When a strong professional relationship exists between the criminal defense lawyer and the expert, it is possible to increase the chances of success in admitting the expert’s testimony.

Reliability in Methods

No matter which field of study the expert has in his or her background, his or her methods of forming an opinion
or connecting evidence must have a certain reliability. In scientific terms, the margin of error when using science procedures should be less than five percent. This should also remain relatively similar throughout all processes completed during the case. Matching the reliability shows the judge and prosecuting lawyer that the expert may have methods that work and could ensure similar results. His or her testimony should also match testing, evidence and proof of the case.

Relevance in the Subject Material

When an expert witness becomes part of legal proceedings, he or she needs to have a subject relevance to the case. This requirement may disqualify the professional if he or she has an educational or expertise background too far from the subject in the court event. An example would involve an environmental crime that led to illegal activity with a professional hired that has a background in administrative work. If his or her experience is not sufficient in the environmental matters, he or she could face disqualification. To ensure the testimony is admissible, the lawyer hiring him or her needs to confirm a relevance to the subject material in the case.

Peer Review and Reliability

For methods to match the necessary requirements in a criminal case, the expert witness must use testing methods that are reliable. For successfully winning a Daubert challenge, this would require the professional to have his or her procedures proceed through a peer review with an acceptable method for scientific processes. Additionally, his or her opinions and conclusions must draw from these procedures. To remain relevant and reliable in the case, a peer review must accept the results and validate the testing processes in full to include the margin of error. If these tests are still in the process of perfecting, the expert may face disqualification.

The Written Report in Criminal Proceedings

While not all cases require a written report from an expert witness, criminal cases usually need this document. The report has several sections, and contents should have the credentials of the professional along with his or her entire process from start to finish. The conclusion generally has his or her opinions about the subject matter and the clear outcome of what he or she believes should occur. Anything the witness will present and express to the court should exist in the written report. The data of the case and everyone involved such as other witnesses, the defendant and the prosecution are necessary.

The testimony of the expert relies on what is within the written report. Often, this document will have several or dozens of pages. The methods used to provide testimony and visual aids are generally within the pages. These visual aids assist the courtroom to understand the evidence or methods better. They frequently also unravel a confusing issue. If civil litigation is possible for compensation, the expert may also explain this in the report. Before adding any details and communication with the lawyer, the expert may need to review the data thoroughly first.

The Testimony in a Criminal Case

Experts present testimony after providing the judge and lawyer with a written report. He or she will explain how the defendant is not guilty of his or her actions and why he or she should not face conviction.

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Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer.

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