The 21-year-old man accused of killing seven and wounding dozens more at an Independence Day parade in Highland Park has pleaded not guilty to all 117 charges.
Robert E Crimo III appeared in Lake County circuit court in Illinois on Wednesday for arraignment where he entered the formal pleas.
In late July, Lake Country prosecutors charged Crimo with 21 counts of murder, 48 counts of attempted murder and 48 counts of aggravated battery, representing the seven people killed and dozens wounded in the attack.
The 21-year-old was already facing life in prison without the possibility of parole after he was charged with seven counts of first-degree murder one day after the Independence Day mass shooting.
Mr Crimo allegedly confessed to carrying out the attack when he was arrested and admitted that he had considered staging a second mass shooting in another state.
During a seven minute appearance, Judge Victoria Rossetti asked whether Mr Crimo understood the charges against him.
Police blocked off roads outside the Lake County Courthouse, which is situated about 16 miles north of where prosecutors say Mr Crimo carried out the mass shooting at the parade in downtown Highland Park.
His next court date is scheduled for 1 November.
This week, 8-year-old Cooper Roberts, whose spine was severed in the shooting, moved to a rehabilitation-focused hospital after spending nearly a month in a Chicago paediatric intensive care unit, his parents said in a statement to the Associated Press.
Cooper has undergone at least seven surgeries and is paralysed from the waist down.
The seven victims in the deadly attack were Katherine Goldstein, 64; Irina McCarthy, 35; Kevin McCarthy, 37; Jacquelyn Sundheim, 63; Stephen Straus, 88; Nicolas Toledo-Zaragoza, 78, and Eduardo Uvaldo, 69.
