Nearly 1,000 people were shot and killed by the US police in 2015, sparking protests and huge controversy. But a new solution promises to reduce the death toll, by focusing in on the key moment of stress in which guns are discharged. Studies have looked at police officers' reactions in these situations - including their stress levels and their implicit biases.

Now, a new training system has been developed which uses heart rate monitors and breathing exercises to minimise the stress reaction. World Hacks investigates whether the system works, and whether it will help save lives. Presented by Sahar Zand.

(Photo: Police stand guard near Trump Tower on Election Day. Credit: Spencer Platt/Getty Images)