If JP Morgan loses a current class action suit, big banks may have to take more responsibility for informing their clients when a deal or a financial instrument raises red flags. New documents have surfaced in a class-action suit a group of pension funds is leading against JP Morgan. They show that during the financial crisis, JP Morgan executives realized a certain investment entity called Sigma was going under. They hedged their own bets, but didn't let their clients — the group of pension funds now suing — know of the danger. If JP Morgan loses this case, big banks may be obliged to intervene in such matters. Louise Story, whose piece on the suit was just published in The New York Times, tells us more.