Lawyer Ed Genson argued it would be illegal for the committee to use material from government wiretaps, and he objected to the panel's rules, saying they don't provide a clear standard for deciding whether to recommend impeachment.
Genson told the impeachment panel that some of its members have made statements suggesting they'd already made up their minds. He also said neither the law nor the constitution spell out the standard for impeachment or what evidence should be considered.
"I would suggest on behalf of Rod Blagojevich that ... those two matters be dealt with," Genson said.
The chairwoman, Rep. Barbara Flynn Currie, rejected Genson's challenges and said the committee rules "will be fair and open." The committee will recommend to the full House whether to move forward with impeachment.
Currie, D-Chicago, noted the panel has wide latitude on how to handle evidence.
"We're not a court of law. We're not quite a grand jury," Currie said. "We're not bound by specific rules of evidence."
The top Republican on the panel, Rep. Jim Durkin, said members must not be swayed by their personal feelings about the governor.
"It's important that all of us put those attitudes, those prejudices aside," Durkin said. "We should not prejudge at this moment."
Genson also is asking the state to appoint and pay for Blagojevich's attorneys in his criminal and impeachment cases. That normally would be Attorney General Lisa Madigan's job, he said, but she can't do it because she has asked the state Supreme Court to declare the governor unfit to serve.
Madigan's office said it will respond soon to Genson's request.
Blagojevich emerged from his Chicago home Wednesday morning for a jog and said he's ready to discuss his case.
"I can't wait to begin to tell my side of the story and to address you guys and, most importantly, the people of Illinois. That's who I'm dying to talk to," he said. "There's a time and place for everything. That day will soon be here and you might know more about that today, maybe no later than tomorrow."
Blagojevich said he was "in good hands" with Genson appearing at the Capitol without him. Asked about when he might talk, the governor was glib: "Hang loose. To quote Elvis, `hang loose."'
The Illinois Senate adjourned Tuesday without considering a plan to fill Obama's vacant Senate seat through a special election. Republicans accused the Democratic majority of trying to hold onto the seat by denying the public a right to vote.
Blagojevich was arrested by FBI agents last week on charges that include scheming to appoint Obama's replacement based on who offered the governor the best political or financial deal.
Currie has said she's waiting for U.S. Attorney Patrick Fitzgerald to indicate whether the panel will be allowed to hear testimony from certain witnesses without compromising the federal corruption case against Blagojevich. She said she has no idea when Fitzgerald will reply.
Criminal charges aside, the committee will weigh other allegations against Blagojevich. Lawmakers have long accused the Chicago Democrat of abusing his power by spending money without legislative approval, defying legislative orders and denying lawmakers information they should receive.
Associated Press writers Jim Suhr and John O'Connor in Springfield and Michael Tarm in Chicago contributed to this report.