In a rare glimpse of what it might be like to be their clients, Mayer Brown partners Richard Ben-Veniste and Andrew Frey offered some words of wisdom for lawmakers Tuesday on their investigation into Russian interference in the 2016 election.

Ben-Veniste, based in Washington, D.C., and Frey, of the firm’s New York office, spoke at a hearing before the Senate Judiciary Committee’s Subcommittee on Crime and Terrorism about lessons learned in their experiences working on congressional investigations when there was also an ongoing criminal investigation. The lawyers were advising the lawmakers on working with FBI Special Counsel Robert Mueller III as he conducts his concurrent investigation on Russian interference and possible collusion with President Donald Trump’s campaign.