Citigroup Help With Insider-Trading Case Detailed in Appeal This content was published on December 23, 2020 - 13:47 December 23, 2020 - 13:47 (Bloomberg) -- Among the 10,000 emails and other pieces of information that Citigroup Inc. provided to U.K. prosecutors was an item that a pair of convicted insider traders apparently thought was crucial: Two investment bankers co-owned an apartment in the Swiss Alps in Verbier. The link between the two bankers was to form the crux of an ultimately unsuccessful attempt by a former compliance officer at UBS Group AG and a day trader to overturn their high-profile convictions. The appeal cast some light on “some of the murkier aspects” of insider trading, the judges said.