Honestly, maybe. Whilst you may be carrying life-saving equipment, you should not be carrying/using any supplies that you haven't been trained to use.
So yes, you may be liable for any issues that arise in situations that you used your own equipment - same as anything. However, would you rather receive a telling off for carrying a tourniquet than attend the funeral of your colleague after they died from an easily treatable issue?First Line Medic does not accept any responsibility for any injuries or damaged caused by our products. DO NOT USE ANYTHING YOU HAVEN'T BEEN TRAINED ON.