In an interview flagged by BuzzFeed, McCulloch told radio station KTRS that he allowed the witnesses to testify because he wanted to present as much testimony as possible.
The grand jury eventually decided not to indict white Ferguson, Mo. police officer Darren Wilson in the killing of unarmed black teenager Michael Brown.
"I thought it was much more important to present everything and everybody, and some that, yes, clearly were not telling the truth," McCulloch told the radio station. "No question about it."
McCulloch returned to the point several times, describing at least one witness who "clearly wasn’t present when this occurred."
"Witness 40" submitted diary entries containing racist remarks that later appeared to have been fabricated after the fact. There is evidence the person lied about witnessing the shooting by piecing together information based on the officer's already-published account, according to a report by The Smoking Gun.
McCulloch said he had no plans to pursue perjury charges against the witnesses, however.
"There were people who came in and yes, absolutely lied under oath," he said. "Some lied to the FBI. Even though they’re not under oath, that’s another potential offense — a federal offense."
"I thought it was much more important to present the entire picture and say, 'Listen, this is what this witness says he saw,'" he added.
Before he announced the decision on Nov. 24, McCulloch faced scrutiny and some criticism from the Brown family and former prosecutors, both for his personal history and approach toward presenting evidence to the grand jury.