The items included a sexual assault kit that authorities say tied a man to the 2006 rape of a 13-year-old girl.
Cook County Sheriff Tom Dart says his deputies discovered the evidence after they took over the building once occupied by the Ford Heights Police Department. Cook County deputies have been patrolling Ford Heights since most of its police were laid off several years ago.
Dart says handling of the evidence was "outrageous," and it's not clear whether police ever interviewed the girl or read reports about her case.
His department has arrested a 27-year-old man linked to the assault by DNA tests.