Stevens says he asked Allen to oversee the project while he was in Washington, but insists he sought to pay all the bills and had no idea his friend was absorbing most costs himself.

Allen admitted Monday he added some features like gaudy Christmas lights and a stainless steel grill without checking with Stevens first.

"It was too much," Allen said of the lights. "I shouldn't have done that."

The witness testified that he didn't always pay close attention to the project. But he told jurors it was ultimately his responsibility.

"What's the old saying? The buck stops here?" he said.

Earlier Monday, U.S. District Judge Emmet G. Sullivan ordered the government to file a formal response at the end of the day to repeated defense claims that prosecutors intentionally withheld evidence favorable to their client. In an initial filing late Sunday, prosecutors wrote, "Contrary to all of the theatrics and hyperbole from the defense, no one has attempted to hide evidence or hold back any discoverable item."

Sullivan said he would take up the issue as prosecutors near the end of their case, possibly Tuesday afternoon or early Wednesday.

Stevens, a patriarch of Alaska politics for generations, hopes to clear his name with an acquittal before voters go to the polls next month to vote on whether to return him to a seat he's held for 40 years.