A jury in Wilmington, Del., on Tuesday found Hunter Biden, President Biden’s son, guilty of three felony counts for lying on a federal firearms application, a shattering blow for the Biden family in the middle of an unforgiving presidential election campaign. The verdict brought an end to an extraordinary seven-day trial that made painfully public Mr. Biden’s crack addiction, reckless behavior and ruinous spending — narrated by three former romantic partners, including the widow of his...