In a videotaped deposition on behalf of the tobacco industry in 2014, Professor John Geer, a political scientist at Vanderbilt University, was confident in citing public opinion about smoking. “I have studied a lot of polls, and I’m confident of my opinion of the public being broadly aware of the dangers of smoking by the mid-1950s. The data are rock-solid clear,” he said.

The kicker? Geer may have been a political scientist, but the polls he was talking about were disputed and he is no authority on research in this area. Geer is not the only academic who has testified as an “expert” on behalf of the tobacco industry, a recent story by NPR reveals.

To find out more about how the tobacco industry has been trying to rewrite history — and why academics testify on their behalf — I decided to call Robert Proctor, a history professor at Stanford University who has devoted four decades of his career to reveal the tactics used by the tobacco industry to mislead the public. Below is an excerpt from our conversation. The interview has been edited for length and clarity.

Can you tell me a little bit more about your research into the tobacco industry and its impact on the world in terms of rewriting history?