Smith fielded questions on Thursday from the Republican-controlled House Judiciary Committee about his two criminal cases, which he dropped after Trump won the 2024 presidential election.
One case accused Trump of conspiring to overturn his defeat in the 2020 election, while the other accused him of unlawfully holding onto classified documents.
The hearing marked the first time the American public heard at length from Smith, whose historic prosecutions dominated Trump's years out of power and helped fuel the Republican president's quest for retribution since returning to office.
Smith told the panel he expected Trump's Justice Department to try to bring criminal charges against him.
"President Trump was charged because the evidence established that he willfully broke the very laws that he took an oath to uphold," he told the House panel.
"If asked whether to prosecute a former president based on the same facts today, I would do so, regardless of whether that president was a Democrat or a Republican."
After the hearing, Trump reiterated his calls for Smith to be prosecuted, writing on social media that he had "destroyed the lives of many innocent people".
Republican lawmakers sought to discredit Smith's investigation and buttress Trump's claims the probes were an abuse of the legal system.
"It was always about politics," Representative Jim Jordan of Ohio, the Republican chair of the Judiciary Committee, said at the start of the hearing.
"To get Donald Trump, they were willing to do just about anything."
Smith said the records were necessary to examine Trump's efforts to pressure Republican lawmakers to block certification of the election. He said he had "grave concerns about obstruction of justice in this investigation, specifically with regards to Donald Trump".
Smith's testimony focused primarily on the case that accused Trump of using false voter fraud claims to obstruct the certification of election results following his 2020 defeat to Democrat Joe Biden. He told lawmakers that Republican witnesses, especially those who informed Trump that his fraud claims were not true, would have formed the core of the case had it gone to trial.
"Our investigation revealed that Donald Trump was not looking for honest answers about whether there was fraud in the election," Smith said.
"He was looking for ways to stay in power."
A federal judge has barred the Justice Department from disclosing many of the details surrounding Smith's second case, which accused Trump of stashing highly sensitive government documents at his Mar-a-Lago residence following the end of his first term in 2021.
Trump pleaded not guilty to all charges and has repeatedly argued the charges were improperly aimed at damaging his 2024 campaign. Neither case reached trial and Smith dropped them after Trump won re-election, citing a Justice Department policy against prosecuting a sitting president.
The Trump administration has fired dozens of Justice Department lawyers, FBI agents and staffers who worked on the investigations.
Democrats defended Smith as an apolitical career prosecutor who was guided by the evidence in building his cases against Trump.
Representative Jamie Raskin of Maryland, the top Democrat on the panel, said Trump has assailed Smith "not because you did anything wrong, but because you did everything right."
"You had the audacity to do your job," Raskin said.
with Reuters
