Scientific Evidence

Author:Jeffrey Lehman, Shirelle Phelps

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Evidence presented in court that is produced from scientific tests or studies.

Scientific evidence is evidence culled from a scientific procedure that helps the trier of fact understand evidence or determine facts at issue in a judicial proceeding. Under rule 702 of the FEDERAL RULES OF EVIDENCE and similar state court rules of evidence, "a witness qualified as an expert by knowledge, skill, experience, training, or education" may testify and offer opinions in court if "scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue." Article VII of the Federal Rules of Evidence contains other rules on EXPERT TESTIMONY and scientific evidence. All states have rules on expert testimony and scientific evidence that are similar to the rules in article VII.

Expert testimony on scientific evidence is different from ordinary testimony from laypersons. A lay witness may testify to inferences and give opinions only if they are rationally based upon the witness's perceptions of the subject of the testimony. Experts, by contrast, may give opinions and testify about possible inferences based in part on information obtained from secondhand sources and not from observation of the object of the testimony. For example, a layperson would not be allowed to take the witness stand and offer an opinion on a plaintiff's injury unless the individual had witnessed relevant information regarding the injury. However, a doctor who is certified as a specialist in the particular injury could take the stand and offer opinions on the injury based not only on an examination of the plaintiff but also on secondhand information that is normally relied on by experts in that particular field of medical study.

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One of the most important issues that arises in expert testimony is which scientific procedures a court should accept as evidence. Many scientific procedures are not seriously in dispute and are accepted by courts with little or no inquisition into their validity. Examples include fingerprint tests for purposes of identification, blood tests, breathalyzer tests for alcohol consumption, and ballistics tests of bullets and their impact areas. These scientific procedures are so widely accepted that a court may take JUDICIAL NOTICE of the procedure's validity. Judicial notice means that the parties in the case do not have to present evidence to the court to establish the validity of the scientific procedure. In some instances legislatures have specifically authorized the use of scientific tests, such as breathalyzer tests for suspected drunk drivers.

Whether they are judicially noticed or legislatively mandated...

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