. >> reporter: sari horowitz and her "washington post" colleague scott higham published an explosiverticles questioning why the metro pd hadn't pursued guandique harder in the levy case, given his disturbing m.o. >> he would sit at a park bench and when he saw a certain type of female, something inside of him would compel him to give chase. he would sprint up behind them, grab them around the neck and pull them off the trail. >> i had seen an article in the "washington post" that talked about this guy called guandique, who attacked two women in the park. the microgeography was identical. so i was curious, how, how have they dismissed him? >> reporter: why would somebody who attacked a woman and possibly even killed her, come back to the same area and attack two more women right after that? >> because it worked for him. >> reporter: guandique is hit with a ten-year sentence for the attacks. but now, after the scathing "washington post" articles, police look at the levy case with fresh eyes. zeroing in on guandique's activity around the time chandra vanished. >> we know he didn't go to

the real victim is chandra and her family. >> reporter: the reporters sari horwitz and scott higham wrote a book about the tangled investigation called "finding chandra." both insist the misguided focus on condit is the reason levy's killer is not behind bars. >> from the beginning to the end, terrible mistakes by police and prosecutors. and in the end, no justice. >> reporter: the investigation is described to "20/20" as open but not active. the last h precious golden clue. >> her ring is still missing. guandique may have sold it or gave it to somebody. hopefully they'll watch this program and let the police know. >> whoever has that ring knows something about her disappearance and murder. >> reporter: finally, chandra's parents, deprived of their daughter, deprived of justice, find some comfort in spiritual hopes. are you preparing for the know what happened to your daughter? >> one day i will be with my daughter, and whether we'll get the answer from god or not, i don't know. >> we'll find out then. >> and then maybe what chandra would have said is, "what difference does it all make?"