The entire thing was a hoax to jump start her presidential campaign.
Cory Booker was in on it too, if I remember correctly.
A proper investigation of the crime here would have looked into that. It was clearly staged for her benefit, and she was probably in on it. She had no legislative accomplishments other than a symbolic anti-lynching law.
She was sponsoring an antilynching law in the senate and this hoax was coordinated with her to try to gain attention for the law. unneeded since the last actual racial lynching was in the 1950s.