It happened again on Friday, during a wide-ranging conversation with CNN’s Anderson Cooper on Attorney General Jeff Sessions, WikiLeaks founder Julian Assange and Trump. At one point, Cooper said he had questions about Stone’s polonium assertions.

“I was extraordinarily ill,” Stone told Cooper, before referring to pictures of his face during the period. “You can see in the file footage that you used at the beginning of the segment that I still have lesions on my face from that illness. My doctor believed I was poisoned. They believed initially that there was some radioactive element to that. I’ve never been this sick in my life.”

But Stone wouldn’t go into detail when Cooper asked for proof, even when the host insisted that “polonium poisoning, that would be a huge issue in the United States if someone was poisoned with polonium.”