Sen. Roland Burris (D-IL) claims he has proof he never made an inconsistent statement about his appointment to the Senate, only he can't show it to you.

The proof, his lawyer said, lies in a secret memo that Burris prepared this month. The lawyer, Tim Wright, said the memo will show that the media is responsible for Burris' shifting accounts of how then-Gov. Rod Blagojevich came to appoint him to be Illinois' junior senator.

Just last month, Burris promised to share his proof with the public. On Feb. 17, Burris told reporters there was "never any inappropriate conversation between me and anyone else" leading to his appointment, and the memo showing that would "be provided to the public later this week."

That declaration led us to wind up the ProPublica Promise Clock to track just how long it takes Burris to release the document.

Five weeks later, Wright told us he can't release the recently completed memo because it was prepared for a local state's attorney who's investigating whether Burris committed perjury before an Illinois House of Representatives panel in January.

Burris' testimony (PDF) before the panel was one of several conflicting accounts he gave of his contact with Blagojevich's allies. While facing direct questions from lawmakers, Burris failed to disclose to the panel that he'd expressed his interest in the Senate seat to six Blagojevich insiders, including Rob Blagojevich, the former governor's brother. See our complete timeline of Burris' evolving story here.

John Schmidt, the state’s attorney considering criminal charges against Burris, told us he has received the memo and that his "review still continues." He wouldn't say when the document arrived.

Once Schmidt completes his investigation, Wright told us he would consider releasing the memo, but he wasn't making any guarantees. "It's up to my client," he said.

So the clock ticks on.