Antonio Rodriguez is being held for trial in the November and December killings after a graphic preliminary hearing on Tuesday.
Police say he didn't know the victims’ names but recognized their photos when interviewed after his arrest last month following a DNA match.
The victims, Elaine Goldberg, Nicole Piacentini and Casey Mahoney, are described as women struggling with addiction and sometimes working the streets. Prosecutors say they tried to fight off their attacker.
Detectives who testified Tuesday say Rodriguez said he used a condom in the attack on Mahoney because he knew police were looking for a serial strangler.