Rousseff, 68, is accused of taking illegal state loans to help bridge budget shortfalls and mask the true state of the economy during her 2014 reelection campaign.
The one-time Marxist guerrilla, who was imprisoned and tortured under Brazil's military dictatorship in the 1970s, says the charges are trumped up and amount to a rightwing coup.
Former economy minister Nelson Barbosa and Rio State University law professor Ricardo Lodi were the final defense witnesses brought to testify that Rousseff did not break the law or harm the economy, which is now in deep recession.
The same argument was delivered yesterday by a first batch of Rousseff witnesses who said that such budgetary maneuvers have long been common practice and that Brazil's economic decline was entirely unrelated.
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Her accusers laid out their case on the trial's opening day Thursday, arguing that Rousseff was criminally irresponsible and helped run once booming Brazil into the ground.
Tension is building ahead of Monday when Rousseff, from the leftist Workers' Party, will take the stand for the first time and face her accusers.
The once all-powerful pair are now demonized by the right, blamed for Brazil's economic shambles and tainted by the revelation of a gigantic corruption scheme at state oil giant Petrobras which peaked during the Lula presidency.
Lula's presence and Rousseff's allegations of a plot to destroy 13 years of Workers' Party rule will make for a highly charged atmosphere in the deeply divided Senate where a shouting match broke out yesterday, forcing the session to be suspended.
Two thirds or 54 out of the 81 senators must vote for impeachment to force Rousseff's immediate removal. The latest estimates by opposition senators and major Brazilian newspapers is that the pro-impeachment side is on track to win.