Ex-Merrill Star Trader Semerci in Focus Again at Cum-Ex Case (1)

Osman Semerci, a once-rising star at Merrill Lynch & Co.until the unit he oversaw helped usher in the firm’s demise, is in the spotlight again.

Authorities charged Semerci and three other people linked to the London-based asset manager Duet Group last year for their involvement in Cum-Ex, a stock-trading strategy that exploited gaps in how Germany collected dividend taxes. They are accused of participating in a scheme that generated more than €92 million in allegedly illicit tax refunds in 2010.

In addition to Semerci, who was a partner and chief executive officer at Duet for several years following ...