Which handgun would you recommend to someone with little or no firearms training or experience, for home protection?

I wouldn't recommend any firearm to someone who has little to no firearms training. The possibility for something to go wrong here is too great. My recommendation would be to start taking some classes at a local range or shop. Most have introductory classes for beginners and some offer classes to help new shooters select a firearm they're comfortable with. The training should happen BEFORE the firearms purchase. After that, it's simply a matter of what they're comfortable with. The debates will rage on about what's best; rifle, shotgun, or handgun. They'll just need to educate themselves on the subject and make an informed decision.

Skip the handgun, get a Mossberg 500 for home defense.

In order:

1) Shotgun (yes, I know it's not a handgun). It is the classic "Point & Click" mechanism. Generally speaking, you don't have to "aim" it, you "point" it, and you can point it from across a room AT the door. and still hit your target. Additionally, the racking of a shotgun has a very "distinct" sound akin to that of a rattlesnake in that it can cause visceral level fear in anyone that is familiar with it's sound.

2) S&W Revolver. (357 magnum). The advantage of revolvers is that you don't have to "clear" them. If you have a "misfire" you just pull the trigger again. Rinse and repeat. A .357 is a pumped up 9mm or .38, but it will give someone a hell of a bad day. Yes you only have 5 rounds, but generally speaking people have an easier time firing revolvers than pistols. Part of it is ergonomics, and part of it is mechanics. An additional benefit of the .357 is the reduced cost of practice (you can supplement training with .38)

3) Glock .40 or 9mm. I like "bigger is better" (my carry is a .45) but 40/9mm are generally the most popular so availability of ammo and accessories can be a big deal. Alternately look at the XD from Springfield (great gun and I like it better than the Glock, but it's just not as wide spread).

Edit: CPT Jack Durish Based on your edit, I provide the following "Better to be tried by 12 than carried by 6."

Taurus is the "farm equipment" of handguns. Inexpensive, reliable, and with good longevity.

However, the logic of having a non-lethal round in the SECOND chamber (remember it spins and the hammer engaged the NEXT round) gets a little more complex. I'd almost recommend and Empty one rather than Non-lethal. That adrenaline rush is going to happen and the trigger is going to be pulled in sequence until an empty chamber is hit, which forces conscious thought.

The first issue is: little to no training. This person should get to the range and spend some time with an instructor on the proper handling and basic marksmanship. After they become safe and proficient with firearms. They should consider a pump shotgun for home defense. The sound it makes is distinct and often times will serve as ample warning to GTFO of the house. Identify the target and point the barrel in the general direction pull the trigger and that should do the trick. If they are looking for a pistol, then they should consider a double action revolver. It is the simplest to operate and offers the least trouble while firing. If you have a misfire then pull the trigger again. But the first thing they should do is get instruction by a professional. If they really want to get some training, have them look into IDPA.

for home protection I'd recommend a pump shotgun, with #2 shot.
The shotgun is much better in the close quarters of a house and #2 shot will take out the perp without gpoing through the walls into the neighbors house.

The simplest and easiest to maintain will be revolver, many options of which can be had from Smith & Wesson. Otherwise, I would recommend that he go to the local gunshot that has a range, and sample their various rental guns until he finds one that's fits his needs. Advise his to stay away from any semi-auto that costs less than $400, as you get what you pay for.

As an NRA certified instructor, I have some don't s and do's. Don't take the salesman's advice. Don't buy a tiny light-weight pistol (recoil bites). Do get training FIRST. Do test fire several choices at a range and buy the one that is comfortable and you shoot well with. Consider the advantages of long guns versus hand guns for where you live (city, rural, apartment) and who else is within range of poorly aimed bullets & shot.

With little to no experience, you would want to go simple. Revolver is probably the best choice for a person new to firearms. A .357 revolver with six rounds is all you should need for home defense. Ultimately the best case would be to have the individual perpetrating the crime to see the firearm, and abandon their intentions. Worst case scenario, .357 is going to make someone regret that they didn't leave when they had the chance.

I had a similar question posed on FB, and I responded that before a person every acquires a firearm for home defense, they need to really consider if they would have the ability to use that firearm against another human being. If the individual does not have the ability to use the weapon when forced, then it becomes a liability that is more likely to harm than help. Once that question is answered, proper training in the use of the firearm is essential. It does no good to have the firearm, have the resolve, but lack the skills necessary to wield the firearm effectively.

The Taurus Judge is illegal in CA because it is considered a short barreled shotgun. Getting one in another state and bringing it into CA is illegal. If he ever used it in self defense he would have a hell of a time defending himself in court for using an illegal firearm. CA is very strict about stuff like that and has jailed people for using what they consider "excessive force" in the act of self defense. I recommend he get advice from a lawyer before purchasing that particular firearm.

Edit: I read far better responses than my own.

1. purchasing a firearm without training is like buying a car without knowing how to drive. Essentially a pointless exercise, unless planning on buying the training at once.

2. I would recommend buying training first. At least the magpul dynamics DVDs (very cheap and effective) then making a more informed decision, art of the dynamic handgun goes into detail on several pistols.

3. I agree on a shotgun as a primary home defense weapon.

4. Revolvers in my mind are a risk, they're good for as many rounds are in the chamber (often a lot less than any semi-auto), unless you're a very skilled speedloader.

5. All that said, recommended purchases: 1. Training 2. Ruger 10/22 carbine (plenty lethal inside of 50m and minimal overpenetration risk, far more accurate than a pistol, no recoil fear) 2. Mossberg 500 or remington 870 (hard to miss, must train to recoil and pump manual of arms, cornering and clearing malfunctions) 3. Glock g 17 (simple out of the box, affordable, moderate level of training required lots of rounds in a small package).