The first warrant for Lee's arrest was issued back in January, but ended up rejected. But the case continued and new evidence incriminating the Samsung head was collected, leading to a second warrant and an arrest.
The list of charges against Lee includes embezzlement, bribery, perjury, concealment of criminal proceeds, and illicit transfer of assets abroad. He is currently held behind bars, and it could be as many as 18 months before his trial commences. Interim, the special prosecutor's office has set their sights on Samsung Electronics president Park Sang-jin, whose arrest warrant has been rejected today.
source: Korea Herald via Android Authority