The term "to a reasonable degree of psychological certainty" is frequently used in forensic testimony, but it presents significant challenges due to its vague and poorly defined nature. While it may sound scientific, the phrase lacks a clear consensus in psychology, leaving it open to subjective interpretation. Forensic psychologists may feel uncomfortable with the term, as psychological evaluations often involve probabilistic, not definitive, conclusions. Although some experts can provide strong, evidence-based opinions using differential diagnosis, the concept of "certainty" in psychology is inherently limited. Forensic psychologists should carefully consider their comfort with this term and be transparent about the limitations of their findings in court.