Actually a 4lbs 1911 trigger versus a 12 glock trigger will cause a huge difference in accuracy in high stress situations. My guess is you have never taken an advanced handgun class that induces high stress/adrenaline into your shooting. If you have then I apologize for the assumption. I can tell you from my personal experience that I have much better hits using my duty 1911 or my Apex equipped MP45 versus a factory XD45 when I have attending numerous handgun classes. Train yourself to keep your finger off the trigger until you are ready to fire and it won't be a problem. Nobody has posted a single case where a trigger job (lightened or just polished) has been used against the shooter in court if it was a righteous shoot.
If you consider IDPA type competition high stress, then yes, I have. I'd say the stress you have in competition is at least as great as anything you can get in a class.
Having said that, I've shot DA/SA pistols, 1911's, DAO Revolvers and Glocks with factory and NY-1 triggers in competition, and I would say there was a negligible difference in my accuracy. With adrenaline pumping, your brain hardly registers a difference between a 4 lb 1911 SA pull and a 10 lb Glock NY-1 pull. Granted I'm not the best shot, better than many, a lot that are better than me, but I can still put holes generally where they need to go. In IDPA style competition, I see a negligible difference. Just punching holes in paper at the range, I'm actually a better shot with my NY-1 G19 than I am with anything else.
And if I'm not mistaken, the high stress/adrenaline in those classes usually comes from doing heavy exercise prior to shooting, which doesn't even get close to emulating what a real shooting is like. IDPA like competition is better as it more closely resembles the stress of a shooting, though even it isn't that close either. Please correct me if I'm wrong about the advanced shooting classes.
Edit: I agreed on an excessively light trigger, but 4lbs+ I see no problems with. I have seen several high quality production 1911's that have 4lbs triggers, does that make them a liability?
Here's the crux of the issue. We're talking about excessively modifying your trigger. The weight of a trigger is arbitrary. Any somewhat experienced shooter would say that a 4 lb trigger is fine since your finger should be off the trigger. But here's two things you haven't considered.
1) Are you absolutely sure that when the SHTF, and you need to draw that your finger will for sure be out of that trigger guard until you're ready to fire? It's easy to say yes when you've never been in a shooting situation (higher stress than anything you can artificially create). But statistics show that in those situations, the finger has a way of prematurely finding it's way into the trigger guard. It's happened to me in competition, and I beat myself up over it.
2) Regardless of facts, lawyers who want you convicted will bend the truth/facts. He can use the fact that you went against the recommendation of the factory and lightened your trigger beyond what they consider safe to paint the picture of you as someone who took your carry piece and made it into a deadly killing machine. This is almost exactly what happened to Harold Fish, except they used the fact he carried a 10mm to prove this point. I'm not saying you'll get convicted (and you probably won't based on that alone), but you will likely have another hurdle to jump in your defense. This means more money you'll have to pay out to your lawyer, and possibly even shelling out money to bring in an expert witness to testify that the trigger job isn't what the prosecutor is making it out to be. Why would you want to give your enemy free ammunition?
People like to hide behind the crutch of, "I need this light trigger to shoot straight!" When some time at the range with a carry piece with a stock trigger will get you basically to the same point.
I'm not a lawyer, and I will tell everyone to take my advice with a grain of salt. But the experts, those who have been a part of cases either as witnesses, expert witnesses, or defense lawyers almost all agree with what I am saying here. If you have trouble hitting a target with a stock trigger, you need more time at the range.
On a side note, no one has posted a case where a trigger job has led to a conviction, this much is true. But the absence of a case now does not guarantee it will never happen. Prior to Harold Fish, there was no case where someone was convicted almost solely on the fact he used a 10mm...yet 2 separate criminal trials and 3 years in prison for a clean shoot have proved my statement here.
Also, I can surmise that although these things haven't led to a conviction, they have been brought up against someone. We don't hear about it because it becomes a non-issue. BUT it's another hurdle you have to jump in your defense.
Have you also considered the possibility that most people don't modify their triggers and there are too few cases of a self defense shooting with a modded trigger because of this? No one I know personally who carries, or has a HD pistol has the trigger modded. It seems that the majority here won't do it on a carry piece either. I would imagine most of the public wouldn't either. I wouldn't want you, or anyone on this board to be the test case.