Credibility assessment examines consistency, demeanor, corroboration, bias, and plausibility. Internal consistency across depositions, medical records, and trial testimony matters greatly. External consistency with physical evidence and witness accounts adds credibility. Demeanor includes eye contact, hesitation, and emotional appropriateness. Financial interest in outcomes creates bias requiring acknowledgment. Prior dishonesty including criminal history may impeach credibility. Detailed memories of traumatic events seem more credible than vague recollections. Cultural factors affect demeanor interpretation. Jury instructions guide credibility determinations. Successful plaintiffs acknowledge weaknesses while maintaining core truth. Professional witnesses face higher scrutiny than occurrence witnesses.