O'Neill has been with department for dozen years

The Justice Department has named a new top merger-vetting official.

Antitrust chief Makan Delrahim has named section chief Kathy O'Neill to a new post as senior director of investigations and litigation.

As such she will be the most senior civil antiturst attorney. Most recently, she had been chief of the Antitrust Division’s Transportation, Energy and Agriculture Section.

O'Neill has been with the antitrust division for a dozen years. Before that, she was assistant attorney general for New York State and was an attorney adviser to the FCC.

Among the merger reviews in which she played a "leading role" was AT&T's unsuccessful effort to buy T-Mobile in 2011--Justice sued to block the deal.