You may not have heard of Joshua Mitts, a young Columbia University professor who is making some powerful enemies on Wall Street.

The 36-year-old securities law specialist has become an increasingly influential figure in the hot debate over activist short selling since publishing a 2018 analysis of trading data that suggested some players were manipulating the market.

Interviews with 12 people familiar with his work and career, including Mitts himself and some of his toughest critics, shed light on how an academic little known outside his field just a few years ago has since taken center stage in the ugly feud between short sellers and the companies they target.