Bo Rupp's family say the drink contributed to the boy's death last September.
The boy's mother wants the drink banned. Her attorneys believe that the drink maker, Phusion Projects, was careless and negligent when it formulated the product.
"I am here today to help save kids lives from dangerous products like this," said Karla Rupp, Bo Rupp's mother. "While I don't approve of underage drinking of any kind I believe that if my 'BoBo' had celebrated with more conventional drinks, he would have passed out and ended up with a bad hangover."
The 15-year-old drank two Four Loko drinks he bought at a Virginia convenience store. He went to a concert, but concert staffers called Bo's mom because he was acting strangely. She picked him up early and struggled to get him home.
Bo was seen walking against highway traffic when he laid down or fell and was hit. He died the next day.
"The young man was so poisoned by the drink he simply ran from the car," said Jeffrey Simon, Rupp's attorney.
"The kids they don't understand. They don't understand 12 percent alcohol. They don't know what that means," said Rupp.
Attorneys for the family say Four Loko is a dangerous concoction, which was formulated by Phusion Projects as a malt liquor with caffeine added. They claim the original formula Bo drank serves up the buzz of nearly a six-pack of beer and is marketed in a variety of fruit flavors that appeal to young people.
This is the first lawsuit filed in Cook County Circuit Court that is aimed at the Chicago-based company.
"Why did we file the case here in Chicago when these events occurred in Virginia? Because that's where Phusion Projects is. That's where the founders are," said Simon. "We have brought this fight to their doorstep. If they are right about the product, they can defend it in their backyard."
Fearing a federal ban, last year Phusion Projects decided to reformulate its drinks by decaffeinating them. The Illinois Senate banned caffeinated alcoholic beverages last December after intense public attention to Four Loko.
Regardless of the ban, Bo Rupp's family believes the reformulated product is still too dangerous to be on store shelves.
The Phusion Projects say they changed their formula and e-mailed a statement to ABC7 saying in part: "We are extremely saddened by this tragedy and our thoughts are with the Rupp family. This accident, and others like it, speak to the serious, societal concerns regarding the misuse of alcohol, alcohol abuse and underage drinking."