The testimony of expert witnesses often is the most critical evidence used to determine the outcome of cases alleging construction defects or failure. There are questions and issues only an individual qualified as an expert witness can address in construction and professional liability cases, such as:
Only certain witnesses are allowed to present expert testimony, and their opinion testimonies must be reliable. Only an individual with expertise in the field is allowed to present opinion testimony regarding subjects that are beyond the common knowledge of lay persons.
Unlike expert witnesses, the admissible testimony of a witness who is not qualified as an expert generally is limited to factual testimony based on personal observations and knowledge of the events and transactions that are the subject of the litigation. Per the Federal Rules of Evidence that govern cases in federal courts and are followed in most state courts, a lay witness can offer an opinion only in limited circumstances where the opinion is rationally based on the witness's perception and is helpful to understanding the witness's testimony or determining a fact in dispute. If the witness's testimony is based on scientific, technical or other specialized knowledge, the witness must be qualified as an expert in the field and his or her testimony must satisfy the standards required of experts for reliability.
Construction cases often become battles of experts. The expert witness who is better prepared, more familiar with the facts of the case, more experienced and knowledgeable in the field, and better able to explain his or her reasoning is more likely to be the more persuasive witness whose testimony could determine the outcome of a case decided on technical grounds. If an expert is found not qualified or the expert's testimony is found inadmissible, the party intending to have the expert testify on their behalf is likely to lose the case perhaps through entry of summary judgement.