The only time that would come into question would be a "bad shoot" situation. Example: your Glock came with a 5lb. trigger and you replace it with a 3.5lb. trigger. You are in a tense situation and have an accidental discharge and shoot an innocent bystander. Or you are holding a bad guy, who has surrendered, at gunpoint and has no weapon, you are nervous and shoot him with an accidental discharge. A case could be made that your modification contributed to the "bad shoot". Proof? That's why NYC Cops are required to have 8lb. triggers in order to prevent such occurrences.