Think of it like needing a mechanic to sign off that a car problem is real before a warranty fight can seriously move forward. In legal cases, an expert affidavit requirement means a person bringing a claim must file a written statement from a qualified professional early in the case, saying there is a reasonable basis to believe the defendant failed to meet the proper standard of care and caused harm. In injury cases, that professional is often a doctor, engineer, or other specialist. The affidavit helps screen out weak claims and shows the case is backed by more than suspicion.

Practically, this requirement can affect timing, cost, and whether a case survives at all. If a required affidavit is missing, late, or signed by someone unqualified, the court may dismiss the claim. In medical negligence cases, it also shapes how lawyers investigate, because they often need medical records reviewed before filing.

Indiana is a little different. Indiana generally does not use a traditional expert affidavit requirement at the start of a medical malpractice lawsuit. Instead, under the Indiana Medical Malpractice Act and Indiana Code 34-18, most claims against qualified healthcare providers must first go through a medical review panel after a proposed complaint is filed with the Indiana Department of Insurance. Even without an upfront affidavit, expert support still matters. A strong expert opinion can help prove causation, meet the standard of care, and improve settlement leverage.