With the star witness against Sen. Ted Stevens due to testify Tuesday, prosecutors denied allegations they secretly shuttled another key witness back to Alaska so he wouldn't hurt their corruption case against the lawmaker.

The government claims in newly filed court papers that Robert Williams — manager of a makeover of Steven's cabin that's central to the case — needed to go home before the trial started last week to get medical help.

When prosecutors met with the 58-year-old Williams to discuss his possible testimony at Stevens' trial, he "appeared jaundiced, his face was gaunt, he had substantially aged, he had chronic coughing spells and he was frequently short of breath," the papers said.

Stevens' attorneys have accused prosecutors of trying to hide Williams after realizing he had information that could help the defense. On Monday, the judge demanded an explanation of why they didn't tell anyone that the witness, who was subpoenaed by both sides, was gone.

Prosecutors, in their papers, said that Williams left messages with the defense team before leaving Washington, and still might return if cleared by doctors.

"The government was primarily concerned with Mr. William's health," the papers said.

Stevens, 84, is charged with lying on Senate financial disclosure forms about more than $250,000 in work done on his hillside cabin and other gifts he received from VECO Corp., a powerful Alaska oil pipeline contractor. On Tuesday, jurors heard testimony from VECO employees and other witnesses who did work on the home, including a stained-glass artist testified about making a window for the home.

VECO owner Bill Allen is scheduled to take the witness stand later Tuesday in what will likely be the highlight of the trial of the Senate's longest-serving Republican. He is expected to testify that he lavished Stevens with the free house renovations — a balcony, a new roof, a custom steel staircase with handmade railings — and other gifts.

Stevens didn't report any of it on his Senate financial disclosure forms, an omission that has landed him in a Washington courtroom while his Democratic opponent, Anchorage Mayor Mark Begich, is campaigning against him in Alaska.

Just as Allen's testimony is key to the government's case, discrediting him is essential for Stevens. The senator insists he never asked Allen for any free work and thought his friend was sending him every bill for the job. Stevens and his wife say they paid $160,000 for the project and assumed that covered everything.

Stevens says that if freebies were tacked on to the job, Allen did so without telling him. Because the senator's wife handled all the finances, he says there's no way he could have known Allen was adding on work.

Allen has pleaded guilty to bribing Alaska lawmakers and, as part of his plea deal, became a crucial FBI witness in a corruption investigation that has rattled Alaska's political system.