Army veteran Raymond Morua was employed as a field director for Capps (D-Santa Barbara) in December when he hit Mallory Dies, 27, as she crossed a street in downtown Santa Barbara, according to Santa Barbara Superior Court documents.
Morua pleaded guilty to gross vehicular manslaughter while intoxicated, among other charges, and was sentenced in May to 20 years to life in state prison.
The Justice Department's probe began after Santa Barbara Dist. Atty. Joyce Dudley sent a five-part newspaper series from the Santa Barbara News-Press to the U.S. attorney for the Central District of California in Los Angeles.
"Our office welcomes the DOJ's inquiry, which will enable the community to move past the false allegations asserted in tabloid media coverage," a statement from Capps' office said, referring to the News-Press' articles.
The Times was unable to reach the Justice Department for comment.
In April, Matt and Raeona Dies filed a wrongful death lawsuit against Morua, Capps and the U.S. government, claiming the congresswoman hired the aide despite being aware that he had previous drunken driving convictions and that he was on the clock when the accident occurred.
According to court records, Morua had two prior DUI arrests, a hit-and-run and an embezzlement conviction.
Capps is facing a tough reelection fight in her district, which includes Santa Barbara. Votes from the June 3 primary are still being counted to determine her opposing candidate for November.
Capps' office said staffers did not know of Morua's criminal history when he was hired, and have since decided to "implement even stronger requirements and worked with U.S. Capitol Police to conduct criminal background checks on all current employees" and future potential hires.
As for the night of the incident, Capps' office says Morua wasn't on official business.
"To be clear, Raymond was attending [a] holiday party of his own volition; he was not asked to attend and had no official role on the congresswoman's behalf at the event," according to the statement.