In Reasonable Scientific Certainty, document examination expert witness Dennis Ryan writes:
A recent report by the Criminal Justice Section of the American Bar Association (ABA) to their House of Delegates addresses the common term “Reasonable Scientific Certainty.” This term or a variant of the term has been seen frequently in many expert reports and has been called a requirement by many who use our expert reports. The ABA report recommends that this phrase be avoided because it has no scientific meaning.
The ABA report calls this term ambiguous and it appears to be used to measure the degree of confidence of the expert in his or her conclusions. This ambiguity can cause the expert’s conclusions to be misinterpreted by anyone that reads the expert report.