It was error for the trial court to have applied a preponderance of evidence standard to appellant’s duress defense in a robbery trial. Since duress negates the mens rea element of the crime, the defendant need only raise a reasonable doubt that he acted under the exercise of his own free will. However, reversal was not required because based on the entire record, the error was harmless beyond a reasonable doubt. The trial court found that appellant had the opportunity to alert the authorities, which condemned his duress defense. Under those circumstances, the trial court’s application of an incorrect burden of proof was inconsequential.