Christian Deslauriers appeared in court Monday on behalf of Brazeau, as the case was put over until April 28.
"I expect this case to be quite voluminous and complex," Deslauriers said outside the Ottawa courthouse.
Crown prosecutors disclosed a file of information to Deslauriers, but he said he expected more to follow.
Brazeau and retired Liberal senator Mac Harb are facing charges of fraud and breach of trust in connection with the Senate expenses scandal.
Both men are accused of claiming expenses for a secondary residence in Ottawa, even though they lived primarily in the national capital region.
Where Brazeau resided — and the rules governing housing expense claims — could be key to determining his innocence, his lawyer said.
"One of the notions that will have to be explored is the notion of residence," said Deslauriers.
"Permanent residence, secondary residence are notions that will have to be explored and these notions in law are very complex issues."
Harb's lawyer is expected to appear in court Tuesday on his behalf.
Both men are accused of defrauding the Senate of more than $5,000.
Harb and Brazeau have maintained they did nothing wrong and that the rules regarding primary and secondary residences are unclear.
Nevertheless, Harb has repaid the Senate almost $232,000.
Last spring, the Senate ordered Brazeau to pay back almost $50,000. He refused, so the Senate garnisheed his salary until last November, when he was suspended without pay.
Jurisdiction may also be a factor in the case, since an Ontario provincial Crown attorney is acting as prosecutor.
"I was definitely surprised to see the provincial Crown handling (the case)," said Deslauriers.
"Usually when the RCMP is involved, most of the time we see the federal Crown handling the matter.
Harb's lawyer, Sean May, has said he expects the case will be adjourned for several weeks.
Senators Mike Duffy and Pamela Wallin were also suspended without pay for allegedly making fraudulent expense claims. They are both still under RCMP investigation but no charges have been laid against either of them.
Duffy, Wallin and Brazeau were all Conservative senators, but have been dropped from the party.
The RCMP is also investigating Nigel Wright, Prime Minister Stephen Harper's former chief of staff, who personally gave Duffy $90,000 to reimburse the Senate for questioned expense claims.
Brazeau is also facing assault and sexual assault charges in an unrelated case in a Quebec court.
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