With forebears who built a fortune in consumer finance, degrees from Princeton and Harvard, and a string of plum Wall Street jobs to his name, Andrew W.W. Caspersen’s pedigree bespoke wealth and privilege.

But along the way, federal prosecutors said, his life took a darker turn. They allege the 39-year-old private equity executive concocted a phony investment fund, invented a fictitious financier and set up bogus Internet domain names and fake email addresses, all part of a bizarre scheme to steal $25 million.