Tear gas is a chemical weapon banned in war. So why do police departments still use it on civilians in the United States? Producer Linah Mohammad and reporter Devlin Barrett examine the history of tear gas and the ethical questions about its use.Read more:Over the summer, tear gas was deployed to disperse peaceful protesters outside of St. John’s Church near the White House before President Trump posed with a Bible in front of the church, raising questions about the use of the chemical agent by law enforcement. Listen to the audio documentary KUOW at 65: The Battle in Seattle here.Subscribe to The Washington Post: https://postreports.com/offer