The US Court of Appeals for the First Circuit has solidified a circuit split on who has burden of proving loss causation in ERISA breach of fiduciary duty cases. The First Circuit joined the Fourth, Fifth and Eighth Circuits holding that once a plaintiff demonstrates a fiduciary breach, the defendant has the burden to negate loss causation. Other circuits, including the Sixth, Ninth, Tenth and Eleventh Circuits, have held that a plaintiff bears to burden…