Yes there actually is.
If the gun was able to fire by itself, without the trigger being actuated, then someone should make it happen on video. Shake the crap out of it, bang on it. Take it in and out of a clear plastic holster 1000 times until the supposed defect happens.
Here, the police officer isn't even touching his holster.
Regardless, if there is a defect in that particular gun, they should just demonstrate it. If it isn't the holster, or something in the holster pulling the trigger, make it happen outside the holster.