Danna Simpson is the friend of Canadian student Jennifer Durning. She took Jennifer out for clubbing in New York City when they crossed the border to visit during a school trip. Jennifer was out partying and saw Jason King, who was brought there by his cousin Nicky Pratt and Nicky's friend Doug Waverly to have Jason lose his virginity. Jennifer left the club to hook up with Jason.
When she got back to the hotel she was staying at, she was crying in the elevator and later called Dana to tell her what happened: Jennifer and Jason had sex, but then Nicky and and Doug jumped in and gang-raped Jennifer. After taking a shower and leaving her clothes behind, Jennifer disappeared and was presumed to have been murdered.
Jason sold out Nicky and Doug by placing an anonymous call about Doug leaving the country on a private flight, resulting in all the boys being arrested. Dana accounted on the stand to her time around and hearing from Jennifer, and Jason provided his testimony of the playouts of the crimes after charges against him were dropped. When Jason soon after went missing, his and Dana's testimonies, as well as character witnesses, weren't enough to convict Nicky and Doug.
It was revealed Nicky and Doug sabotaged the trial the whole time with the assistance of Nick's girlfriend, court officer Emily McCooper by bugging Judge Donnelly's office and kidnapping and killing Jason to silence him. When he was found in the same place Jennifer was left, Nicky and Doug were arrested for Jason's murder. (SVU: "Gone")