DNA testing was at its infancy stage way back then (1989).
As Ann Coulter, who followed the case closely observed:
The use of DNA to solve crimes was nearly unheard of in 1989. No police force in the country would look for DNA to make a case. It was only about a year earlier that DNA had been used for the first time in any criminal court in the U.S. (Florida).
The very month that the jogger was attacked, newspapers were excitedly reporting on a novel forensic technique, a “still unfolding laboratory discovery, a genetic ‘fingerprint’ created from the body’s deoxyribonucleic acid, or DNA”—as the Chicago Tribune put it.
Even five years later, DNA evidence wasn’t enough to convict O.J. Simpson.
You’re probably correct. It just seems with all the blood, semen, scratches, clothes, etc. that only DNA of the one guy was found. I’m not saying these guys are innocent, I’m just saying it is kind of a hmmmm.