A criminal defendant has the right, under the U.S. Constitution, to confront his accusers. The U.S. Supreme Court has interpreted this right by banning the admission of some categories of hearsay.
In a forensics case, this will impact on whether the testifying expert may utilize and discuss the lab report of a colleague (or of an expert at another laboratory). The problem will also arise if the expert who conducted the testing has retired or is otherwise unavailable. Accordingly, an expert who is testifying, at least in part, on what others have done or reported must make this clear to the lawyers in the case, well before trial, so that the issue of hearsay admissibility can be resolved before the trial.
At the same time, it must be understood that much hearsay is admissible on its own; thus, talking about it during the expert's testimony will present little or no problem. Examples of types of hearsay that are admissible include:
- Certain business records (such as hospital reports).
- Statements made by an individual for the purpose of medical diagnosis or treatment.
- Excited utterances by a crime victim or witness seeking emergency assistance.