From the Appendix to Lauren Sudeall Lucas, An Empirical Assessment of Georgia’s Beyond A Reasonable Doubt Standard to Determine Intellectual Disability in Capital Cases, 33 Georgia State University Law Review 553, 607 (2017).

STATE BURDEN OF PROOF
Alabama Preponderance of the evidence
Arizona Clear & convincing evidence
Arkansas Preponderance of the evidence
California Preponderance of the evidence
Colorado Clear & convincing evidence
Florida Clear & convincing evidence
Georgia Beyond a reasonable doubt
Idaho Preponderance of the evidence
Indiana Preponderance of the evidence
Kansas Not specified by statute or case
Kentucky Preponderance of the evidence
Louisiana Preponderance of the evidence
Mississippi Preponderance of the evidence
Missouri Preponderance of the evidence
Montana None stated
Nebraska Preponderance of the evidence
Nevada Preponderance of the evidence
New Hampshire None stated
North Carolina Clear & convincing evidence (pretrial);
Preponderance of the evidence (sentencing)
Ohio Preponderance of the evidence
Oklahoma Clear & convincing evidence (pretrial);
Preponderance of the evidence (sentencing)
Oregon None stated
Pennsylvania Preponderance of the evidence
South Carolina Preponderance of the evidence
South Dakota Preponderance of the evidence
Tennessee Preponderance of the evidence
Texas Preponderance of the evidence
Utah Preponderance of the evidence
Virginia Preponderance of the evidence
Washington Preponderance of the evidence
Wyoming None stated