James W. Lewis made the comments Sunday on a Cambridge, Mass., community cable television program as he promoted his new book, a self-published thriller about people who die from poisoning. He also refused to discuss reports that Illinois authorities are seeking DNA samples from him and his wife.
"If you could just admit to it, right now, that you actually killed those people, then I might have a big, I might actually be -- could you just do that?" host Roger Nicholson said on the program.
"I think that the only thing I can say to you is that you're totally delusional," Lewis replied.
The FBI took items from his home in February 2009 after launching a "complete review of all evidence" in the unsolved poisoning.
News media have reported that he and his wife were asked for DNA samples during a closed court hearing last week in Massachusetts.
No one has been charged with the deaths. Lewis spent 12 years in prison for extortion after sending a letter to Tylenol's manufacturer demanding $1 million to "stop the killing."
"I never dreamed that it would have any type of impact upon those, the victims. If I had, I would have never written [the letter]," Lewis said Sunday. "I feel for those people every day for the last 28 years."