"The horrible tragedy of Ella Frank’s murder," Lightfoot said during the 2022 budget engagement forum held at Truman College on Thursday.
The flub was criticized by the Chicago Fraternal Order of Police, which tweeted on Friday, that "This is one of those times when words really matter."
The mayor’s office did not immediately respond to Fox News’s request for comment on the matter.
French, 29, was shot and killed on Saturday night during a traffic stop. She is the first officer since 2018 to be killed in the line of duty in the city.
Lightfoot botching her name comes just days after Brown referred to French as "Ella Fitzgerald" twice on Monday.
"The offender who is charged with first degree murder of Ella Fitzgerald," Brown said at one point during the press conference.
"The gun used in this shooting and this murder of Ella Fitzgerald was illegally possessed," he said at another point.
Ella Fitzgerald is the name of an award-winning jazz singer who died in 1996.
The flubs come after Lightfoot received an icy greeting from police officers in the city last week, when she visited the hospital where French’s partner is being treated for critical injuries stemming from the shooting. During the visit, more than two dozen officers were seen turning their back on the mayor as she approached them.
"It looked like it had been choreographed," a source told the Chicago Sun-Times.
The father of the male officer also "excoriated" the Democratic mayor and blamed her for his son’s injuries, according to the outlet.
"In a time of tragedy, emotions run high and that is to be expected," the mayor’s office told Fox News at the time of the incident.
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