When Kashyap Patel was an aide to the House Intelligence Committee in the first years of the Trump administration, he played a key role in helping Republicans try to undermine the Russia investigation, writing a memo that accused law enforcement officials of abusing their power. It made Mr. Patel a hero among Republicans. After they ceded control of Congress this year, he landed on Mr. Trump’s National Security Council staff. Mr. Patel, who is known as Kash, is now assigned to work on counterterrorism issues, not Ukraine. House impeachment investigators are scrutinizing Mr. Patel’s actions. Fiona Hill, the National Security Council’s former senior director for Eurasian and Russian affairs, testified to House investigators last week that she believed Mr. Patel was improperly becoming involved in Ukraine policy and was sending information to Mr. Trump. Mr. Patel’s apparent communications with the president prompted Ms. Hill to raise concerns with her superiors, including John R. Bolton, then the national security adviser, that Mr. Patel was meddling outside his portfolio. Mr. Patel is closely aligned on the National Security Council staff with another alumnus of Mr. Nunes’s committee, Michael Ellis, now a top White House lawyer. Mr. Patel’s role as an investigator for Mr. Nunes is highlighted in a book by Lee Smith, a conservative journalist, set to be published next week. Patel, was born and raised in Garden City, New York to parents with Gurajati roots who immigrated from East Africa — who came to the U.S. by way of Canada in 1970 — and is an alumnus of the University of Richmond (Class of 2002), and according to his Facebook page claims that he earned a certificate in international law from the University College London Faculty of Laws and graduated from Pace University’s law school in 2005, and then spent part of his career in the Miami area as a federal public defender in Florida before taking a job at the Justice Department in 2014.