The plan was for Kang Gao to do his exit interview with Two Sigma Investments LLC, a $21 billion quantitative hedge fund in New York, and jump to Citadel LLC, a rival firm in Chicago.

Gao never got that chance. Unbeknown to him, that final meeting had been recorded for investigators at the Manhattan District Attorney's Office, and instead, the 29-year-old native of China found himself sitting in a New York City jail. He’s accused of stealing Two Sigma secrets and faces a potential four-year prison term.

Gao is the fourth Wall Street analyst or programmer to be ensnared in a crackdown by the D.A., Cyrus Vance Jr., on intellectual property theft from financial firms. His decision to charge Gao, former Goldman Sachs Group Inc. programmer Sergey Aleynikov and ex-employees of the Dutch firm Flow Traders BV, signals a willingness to criminalize financial industry disputes formerly relegated to contract litigation.

The prosecutions come as Wall Street is increasingly protective of intellectual property, including trading models and software code, which have become more valuable as firms seek a millisecond advantage over rivals through strategies including high-frequency trading.