MINNEAPOLIS — When a man regarded as the deadliest sniper in U.S. history detailed his kills in a bestselling autobiography, he also included details about a 2006 incident in which he says he punched a guy he called “Scruff Face” — later identified as former Minnesota Gov. Jesse Ventura.

Ventura said the fight didn’t happen, and he sued author Chris Kyle for defamation. The trial begins Tuesday, and it will be up to Ventura’s attorneys to prove that Kyle’s account about that night in a California bar was false — and even more difficult, that Kyle knew it.

“Ventura is going to have to prove falsity … but the harder part is proving actual malice,” said Raleigh Levine, a law professor at William Mitchell College of Law in St. Paul. “It has to do with what you know about the truth — that you actually knew that what you were saying was false or that you recklessly disregarded the truth.”

Besides sorting out what happened in the bar, jurors will have to assess whether Ventura’s reputation was damaged and whether Kyle used Ventura’s name to make a profit.

Kyle and a friend were killed in February 2013 at a Texas gun range, allegedly by an Iraq War veteran they were trying to help. Kyle’s widow, Taya Kyle, is now the defendant.