Ashtonja Abreu is the daughter of Marianna Abreu, a drug-addicted woman who was a witness to a case Rafael Barba prosecuted. Barba gave Marianna money, which he knew was likely to be used for more drugs, so she could testify and put away a rapist and murder of two girls. Marianna overdosed after the trial, and out of guilt and for the family's low income, Barba's been paying Ashtonja and her grandmother ever since.
David Willard, a rape and murder suspect, found Ashtonja and interrogated her at her doorstep after hacking Barba's files, then threatened Barba with exposure if the case wasn't dismissed. Ashtonja told the truth to Special Victims, and when Barba admitted it, the squad found new evidence to convict Willard on. (SVU: "Know It All")