The Insurer's Duty to Defend: Pre-Suit Demand Letters

Commercial general liability (CGL) policies typically require an insurer to defend any "suit" that seeks potentially covered "damages" that the insured may be "legally obligated to pay." This seems simple enough. But when can an insurer ever have any obligations to its insured before a suit is filed? In particular, can an insurer ever have obligations to defend a pre-suit demand against a claimant? The answer is less straight-forward than it seems. 

Eric Hermanson and Austin Moody discuss an insurer's duty to defend pre-suit demand letters in their article for the American Bar Association's The Brief.