Smith, a sophomore guard, was driving a 1996 Lexus last Monday night when it struck a tree in heavy snow. He then drove the car a little more than a mile to the apartment complex where he lived.
Bystanders called 911 after seeing the badly damaged car in the parking lot, with Smith's passenger, teammate Brian Carlwell, still inside, Champaign County State's Attorney Julia Rietz said. A number of other team members were gathered at the apartment, Rietz said.
"It appears that Smith was distraught, as he believed Carlwell had died in the crash," Rietz said in a written statement.
Smith's blood-alcohol level was .176 after the crash, more than twice the legal limit of .08, Rietz said.
Rietz said university police investigating the accident found that Smith and Carlwell had been drinking tequila and beer with others at an apartment in his complex, and left just after 11 p.m.
Smith lost control of the Lexus _ registered to his grandparents _ which hit the tree on the passenger side, authorities said.
Carlwell, 19, suffered a severe concussion and spent four days at Carle Foundation Hospital Urbana before being released last Friday. He was well enough to sit on the bench at Sunday's game against Northwestern at Assembly Hall, and could play in the postseason, coach Bruce Weber has said.
Smith, a sophomore guard, was taken to the same hospital by unidentified coaches and university police, Rietz said. He was treated for a minor concussion and released early the next morning.
Witnesses reported seeing the Lexus pull into the apartment parking lot, then saw a tall man wearing University of Illinois sweat pants leave the car and enter the apartment building, leaving an unconscious Carlwell in the car, Rietz said. Shortly afterward, the tall man returned with a second man, then left and went back in the building, she said.
Smith was not in custody Tuesday, Rietz said. She said he is expected to appear in court at a date to be set.
Smith's attorney, Mark Lipton, was in court Tuesday and not available for comment, his office said.
Weber criticized his player in a written statement but said he is still part of the school's basketball program.
"This was a case of extremely poor judgment by Jamar," Weber said. "He remains a part of our family and needs us now more than ever."
Aggravated driving under the influence is a Class 4 felony that carries a sentence of up to 12 years in prison. Leaving the scene is a Class 3 felony and carries a sentence of up to five years in prison, Rietz said. Someone convicted of either charge, though, could be placed on probation, she added.
Smith's only previous traffic infraction was a 2004 citation for failure to stop or signal a turn, according to the Illinois Secretary of State's office.
Weber said last week that Smith would sit out the rest of the season, calling it a mutual agreement that would allow Smith to "focus all of his attention on the physical, emotional, academic and other related issues he will face in the coming weeks."
Smith was selected to the Big Ten All-Freshman team last season, leading the conference in 3-point shooting by hitting 48 percent of his 137 shots.
This season Smith had struggled to find his form after a pair of ankle injuries. He hit just 32 percent of his 3-point attempts before leaving the team.
Carlwell has averaged 1.7 points a game as a reserve.
Smith's traffic accident wasn't the first legal issue for the team.
Senior guard Rich McBride was arrested Sept. 29 and charged with driving under the influence. He has not entered a plea in the case, which is scheduled for a hearing on March 1. McBride was suspended or six games early this season because of his arrest.