On Tuesday, a federal grand jury returned an indictment charging Trump with four criminal counts in connection to special counsel Jack Smith's probe into his alleged role in trying to overturn the results of the 2020 presidential election.
"As a DOJ [Justice Department] prosecutor for 25 years, I am very disturbed by this indictment," Sievert said.
"I thought there would be something solid in there, but as I read it, all I saw was that they were indicting Trump for taking a position in the election with which they, the prosecutor and Ds [Democrats], disagreed."
Trump faces one count of conspiracy to defraud the United States, one count of conspiracy to obstruct an official proceeding, one count of obstruction of and attempt to obstruct an official proceeding and one count of conspiracy against rights.
"Despite having lost, the Defendant was determined to remain in power. So for more than two months following Election Day on November 3, 2020, the Defendant spread lies that there had been outcome-determinative fraud in the election and that he had actually won. These claims were false, and the Defendant knew that they were false," the indictment stated.
However, Sievert, who noted he has not supported Trump for the Republican nomination, said the new indictment appears to be criminalizing free speech.
"Whether his [Trump's] belief in fraud was right or wrong, whether the legal theory of sending this back to the states was right or wrong, he had the right under our First Amendment to believe and advocate those positions," Sievert said.
The former prosecutor said he would expect an "objective" judge or judges would throw the case out.
Federal judge Tanya Chutkan, who was nominated by then-President Barack Obama, is assigned to oversee Trump's case. Chutkan is the only federal judge in Washington to issue sentences to convicted January 6 rioters that were longer than what prosecutors had requested, according to media reports.
Trump is summoned to appear in federal court in the US capital on Thursday to face the new charges.