There have only been a handful of investigations into possible criminal conduct by a sitting president of the United States. Each time, an outside investigator has been appointed under a set of rules to ensure independence and accountability — and those rules have changed with each inquiry. Now, the latest set of rules is being tested as the special counsel, Robert Mueller, prepares to release his report. Guest: Neal Katyal, a lawyer who drafted the regulations that govern the special counsel investigation. For more information on today’s episode, visit nytimes.com/thedaily.