Uh, yeah, it's one of the guys himself essentially admitting to the rape by revealing the rest of the story.
Hard to imagine how it would benefit him in his own case to fabricate a story like this.
If he wanted to save himself he'd have kept his mouth shut about all of it.
Now that he's broken the part about Franklin, he and his attorney know Franklin probably won't be too determined to keep anything he might know about the rape to himself.
Possibly...possibly not. He still wasn't there for any of this so this is what he heard happened not necessarily what he knows happened.