Although it took one month of solid, daily searches - Larson discovered the child's remains in the Des Plaines River in North Riverside.
The boy's mother first said he'd been kidnapped, but then admitted she and her boyfriend beat him to death and dumped the body.
Cook County prosecutors say Lakesha Baker and her boyfriend, Michael Scott, have both pleaded not guilty to first-degree murder charges.
Baker is being held without bond. Scott is being held in lieu of $750,000 bond.