Columbia Police are hoping some college students might help break a 20-year-old murder mystery. The investigation has stalled in the murder of Carolyn Williams, who was stabbed to death in her Columbia home on Jan. 2, 1989. Police believe the murder was drug-related, but none of the tips have led anywhere. Now, students in a Columbia College class that studies cold cases have stepped in to help. The class, taught by retired police Detective Mike Himmel, spent 16 weeks looking over hundreds of reports. They narrowed the suspects to six, with two considered prime suspects. Now, investigators will send evidence for DNA testing, which wasn’t available when Williams was killed. Himmel says he believes the case will be solved.