 -- Donald Trump Jr.'s legal team is expanding its operation, bringing on D.C.-based attorney and longtime regulatory lawyer Karina Lynch, his team told ABC News.

Lynch also confirmed to ABC News that she is joining the team.

Donald Trump Jr. is one of the people connected to the Trump administration whom the Senate Judiciary Committee has said it wants to interview as part of its investigation into possible Russian involvement in the 2016 election.

Lynch had been at the law firm Williams and Jensen since 2000, and became a principal in 2005, according to the firm's website.

She "concentrates on legislative, regulatory, and oversight issues affecting various sectors of the health care industry and clients with an interest in education and tax policy," her bio says.

Before that, she spent five years on Capitol Hill, serving as counsel to the Senate Permanent Subcommittee on Investigations, Committee on Government Affairs, which was chaired by Sen. Susan Collins, R-Maine.

She had previously served as investigative counsel for Sen. Charles Grassley, R-Iowa.