<p>The longest running cold case of a law enforcement officer in the United States was the murder of Sheriff's Lt. Joe Clark.</p><p>See Privacy Policy at <a href="https://art19.com/privacy" rel="noopener noreferrer" target="_blank">https://art19.com/privacy</a> and California Privacy Notice at <a href="https://art19.com/privacy#do-not-sell-my-info" rel="noopener noreferrer" target="_blank">https://art19.com/privacy#do-not-sell-my-info</a>.</p>

REOPENED: Missing in Altoona

Based on the iconic, Emmy-nominated series on A&amp;E, this show explores some of the most difficult-to-solve murders, which stymied investigators and went cold, sometimes for decades. In fact, one-third of all murders in America remain open. But thanks to dogged investigators and breakthroughs in forensic technology, these cases become part of the rare 1% of cold cases that are ever solved. Cold Case Files is narrated by Marisa Pinson.