Tiemare Lewis was initially charged with aggravated sexual assault and child endangerment. He pleaded guilty Thursday to criminal trespassing for being in the apartment where the alleged crime took place.
Trenton police initially said the girl took her younger sister to a party and watched as she was raped by as many as seven men and boys last March.
But with no DNA evidence and the 15-year-old changing her story, prosecutors said the case became increasingly weak.
The stepsister and three teenage boys were sentenced to time served and probation after they pleaded guilty to child endangerment or trespassing.