The ongoing investigation surrounding the murder of JonBenét Ramsey turns 20 this year, but she is just one of several famous cases that remain unsolved.
While O.J. Simpson was found guilty of Nicole Brown Simpson and Ron Goldman's murders in the eyes of the civil court, he was acquitted in the criminal trial, which means the murderer is still technically unknown. Theories have been thrown around about Tupac Shakur's and Notorious B.I.G.'s murders, but to this day the investigations surrounding their shootings are unsolved.
Some serial killers, such as the Zodiac Killer and Jack the Ripper, had no problem taking credit for their killings, but the identity of these murderers still remains unknown.
In honor of True Crime Week, E! News is looking at some of the biggest unsolved murder mysteries, so click through the gallery above to see what other cases have gone cold.