A scene outside the courthouse in Peoria - the case had attracted intense media attention in both US and China. [Photo provided to China Daily]

During Bullis' court appearance, Shi gave a written note to a court worker who agreed to pass it on to her. "I told her who I was and what I was doing," Shi said."She contacted me, and we became the very first to film her interview."

According to Bullis, despite speculation that the FBI may have forced or manipulated her, or have paid her, it was she who had asked, from the very beginning, "Is there a way I can help?"

Upon her own request, Bullis sat down with the Zhang family at the end of the trial. Having practiced with Shi, Bullis, who learned Chinese in high school, read a letter to Zhang's parents in Chinese.

"I drew on your love for Yingying to fight off the terror I constantly felt doing what I was doing for the FBI," said Bullis, who burst into tears with relief when Yingying's mother told her that "you are brave and just as kind as my daughter".

On June 24, 2019, the jury convicted Christensen of kidnapping resulting in the death of Zhang Yingying, a crime considered in legal realms as severe as murder.

On his drive back from Peoria to Chica-go, Wang, who had spent a thousand hours on the case, parked his car by the roadside and wept.

Zhang Yingying as a toddler - these days, her loved ones cling to memories of her for comfort. [Photo provided to China Daily]

"Back in 2017, while the family was living in Champaign, Yingying's father took the same daily walks," said Wang, father of an adult son and daughter. "He would walk and walk until, in the far distance, a corner of the student building where Yingying once stayed appeared in sight. There he would stop and stand, sometimes for hours on end, as if waiting."

On July 18 last year after the jury failed to reach agreement over a death sentence, Judge James Shadid sentenced 30-year-old Christensen to life imprisonment without the possibility of parole. Walking out of the courtroom, Hou told the waiting media in English: "For me, the result today seems to tell me that I can kill anyone with all kinds of cruel methods and I will not need to die for it. Me, myself, will never agree with that."