The former McKinsey director accused of passing on confidential information in the Galleon insider trading case is expected to appear in federal court on Thursday.

In court filings last week, prosecutors said they would file an “information” document spelling out charges against Mr Kumar upon his waiver of indictment, a move that some legal experts say suggests he may plead guilty and may be co-operating with the government.

Anil Kumar, allegedly leaked information to Raj Rajaratnam, the billionaire founder of hedge fund Galleon. He has indicated last week that he may waive his right to an indictment, thus enabling prosecutors to file charges against him without presenting evidence to a grand jury.

Mr Kumar, who was accused of passing on information about Advanced Micro Devices, a company he advised while at McKinsey, was among the first to be charged in the insider trading investigation.

Meanwhile, the investigation appears to be gathering pace. On Tuesday, US prosecutors said they planned to expand criminal charges against Mr Rajaratnam, alleging he made at least $36m in illicit profits – more than twice the amount originally alleged – and that in 2006, he obtained confidential information about AMD’s acquisition of ATI Technologies and paid for the information.