He has hired Ashland defense attorney Tony Farese to represent him while they wait on a Pontotoc grand jury's deliberations.
Bostick was arrested Oct. 7 after a vehicle driven by 18-year-old Charity Smith of Okolona pulled out in front of his in Pontotoc County.
Smith was killed and her sister seriously injured in the accident. The Mississippi Highway Patrol report said that while Bostick was driving under the influence, he was not at fault for the accident.
District Attorney Trent Kelly said he cannot speak about secret proceedings by a grand jury, which convened Monday.
But he said "we have the case" and are moving ahead on it.
In January before Barbour left office, Bostick was one of 200-plus pardons and clemencies he granted to people across the state, from murderers to embezzlers.
At the time, Bostick was under arrest for violating his probation, although Barbour and spokesmen in his office claimed not to know that.
Before Smith's death, Bostick had three DUI arrests and was going through a court-mandated drug rehab program. With three DUIs, he faced the possibility of imprisonment.
But Barbour's pardon on the third offense effectively erased it from the record, which meant Bostick was no longer in jeopardy.
A state and national media furor erupted over Barbour's pardons, especially because Barbour is a top Republican Party strategist who flirted for a time with a presidential campaign.
Over the weekend, CNN reported it obtained emails that show Barbour's office was aware of Bostick's October DUI arrest months before the governor pardoned him in his last days in office.
"They knew it, and they didn't stop it," said Charity Smith's mother, Jean, to CNN, referring to the pardon. "Why didn't they do something?"
Smith spoke to CNN, overcome with emotion after reading the emails obtained through a public records request from Mississippi's Department of Archives and History.
The emails show that Amanda Jones Tollison, the governor's chief counsel, and Secretary of State Delbert Hosemann were told about the October car crash that killed Smith, just days after it happened.
Tollison is the wife of state Sen. Gray Tollison of Oxford.
Robert Whitwell, a former assistant U.S. attorney now in private practice, represented Bostick on some of his DUI charges. Later, he asked for long-time friend Hosemann to help Bostick get a pardon.
After the October crash, Whitwell urged Tollison and Hosemann not to support the pardon.
He said Monday the details of the CNN story are correct.
Barbour granted Bostick a full pardon in January for a felony drunken driving offense in March 2009. It was Bostick's third drunken driving arrest in a little more than a year. The pardon gave Bostick back the rights that were taken away as a felon, such as voting, but his two other DUI convictions remain on his record.
In fact, Bostick was in the Lafayette County Detention Center held on the alcohol-related charge from the Smith accident when he was informed about the pardon.
Whitwell told CNN that Bostick is a friend and did good work on investigations while he was with the IRS.
Hosemann reportedly forwarded Whitwell's email to Amanda Tollison, who replied: "OK will do."
Tollison did not reply to Daily Journal questions about the events or communications surrounding Bostick's pardon.
Barbour has repeatedly said he believes in forgiveness and second chances, which guided his decisions on the pardons.