If the armor bar of the Riot Trooper is depleted, their shield will break.
Riot Troopers will also lose their shield and armor if they are sent into the air with a biotic Pull or damaged by the biotic Storm.
Even when they're carrying shields, Riot Troopers can still be knocked off their feet with Slide. Use that to your advantage.
While they're still carrying their riot shields, Riot Troopers will not get into cover as there is no need for them to do so. This changes once they lose them one way or another.
Like other humanoid enemies in the game, these soldiers are vulnerable to headshots, receiving bonus damage when shot there. It is especially powerful if they are carrying their shield but with their head out of cover.
After losing their shield, Riot Troopers will take cover and no longer pursue the player. Use this to your advantage.
The biotic power Leash will always kill a Riot Trooper, due to their low health.