The government contends that no embarrassing photos ever existed. Scott Sippola, however, insists the FBI lost or destroyed the pictures that he planned to peddle to magazines if Stamos didn't buy them.
Sippola offered his defense in a court filing on the same day that a codefendant's deadline for a plea bargain expired. A federal judge had given lawyers until Tuesday morning to iron out an agreement with Allison Coss, but a spokeswoman for prosecutors said nothing happened.
Sippola and Coss are scheduled for trial July 12 in Marquette in Michigan's Upper Peninsula on charges of conspiracy and other crimes.
The FBI says they threatened to sell photos of Stamos unless he paid them off. Coss and Stamos have known each other since meeting in Florida in 2004.
In his filing, Sippola said he had a legitimate deal not extortion in the works and the FBI lost or destroyed the valuable photos after nine agents searched his home last year.
Without the photos, his lawyer, Sarah Henderson, asked U.S. District Judge R. Allan Edgar to dismiss the charges or tell jurors they could consider the lack of photos a strike against the prosecutor's case.
"Without the photographs, the government's case becomes much easier to prove and the defendant's defense much more difficult," Henderson wrote.
Assistant U.S. Attorney Maarten Vermaat said Sippola was raising a "standard defense in blackmail cases."
Stamos' TV credits include "ER" and "Full House."