(CBS) — The family of a Southern Illinois University-Carbondale student found dead in subzero cold more than a year ago gathered with families of other unsolved missing persons and murder cases Saturday in Daley Plaza.

It’s been a frustrating 15 months for Lovely Varughese, whose 19-year-old son Pravin was found dead in a wooded area near Carbondale five days after leaving a campus party. She has never accepted the official explanation that he froze to death after punching an acquaintance in the face and jumping from a car. She believes he was beaten and dumped, and the family paid for a second autopsy that backed up their suspicions, and allegedly showed that he had no drugs or alcohol in his system when he died.

“If you review the first and second autopsies, there is no question that there are problems,” she said.

A week after police pronounced the case closed and the state’s attorney said no criminal charges would be brought, a special prosecutor was named. Varughese said she is encouraged that he asked to see and is reviewing the private autopsy.

The family has sued the city of Carbondale, police and the man they believe responsible for Pravin’s death.

A representative from the office of U.S. Rep. Bob Dold (R-Ill.) attended the vigil. Dold has written the Justice Department asking for a review of the case. Ms. Varuguese will travel to Washington, D.C., in the coming week for a conference and hopes to speak at that time with Justice Department officials.