Backpage announced in January that it was closing its adult section, which included prostitution and sex trafficking ads, but those ads have since moved to different areas of the website, the lawsuit said.
Yoon was found guilty of first-degree manslaughter in June 2017 in Multnomah County Circuit Court and sentenced to 18 years in prison.
Yoon displayed several red flags that should have put hotel staff on alert that he was there to engage in "illegal commercial sex activity," the lawsuit said.
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Representatives for Hilton and Backpage didn't immediately return requests for comment.
The lawsuit claims the hotel chain agreed to train employees to detect and report commercial sex trafficking in 2011, but failed to properly train staff or implement preventative measures to stop sex trafficking and prostitution.
The court papers also cite two cases in December 2011 and February 2014 where Portland police investigated cases of sex trafficking at the northeast Portland Doubletree Hotel, including one involving a man who trafficked Benson.