Fifty top lawyers of major corporations, including Big Pharma, Big Insurance and Big Tech, are urging the federal court system to clarify a rule of evidence that sets standards on expert testimony.

The lawyers, primarily chief legal officers and general counsel, sent a joint letter Monday to the Advisory Committee on Evidence Rules, which is looking at how federal courts address expert testimony and is exploring whether to amend the procedural rule, known as Rule 702.

Expert testimony is required when cases involve "scientific, technical or specialized knowledge" that falls outside the common experience of the jury. Problems arise for companies in cases such as the recent Roundup and talc cancer cases, where federal agencies ruled the products safe but plaintiffs' experts were allowed to testify otherwise.