It is a constitutional question without a clear answer: Can a sitting American president be charged with a crime? The question has new importance as special counsel Robert Mueller investigates the Trump 2016 presidential campaign. He is looking into possible connections between the campaign and Russians who reportedly interfered in the 2016 election. Last week, it was reported that Mueller is using a grand jury as part of his investigation. Grand juries decide if government investigators may legally demand private records and information from witnesses. There was no information about whenor whetherMueller would bring criminal charges in the case. On Wednesday, the Washington Post reported that federal investigators searched and gathered evidence from the house of Paul Manafort, a Trump campaign manager. Mueller can prosecute any federal crimes linked to the investigation. In theory, that could include legal action against the president.