Not that under said situation one would need to see their sights, crisply.
With training one develops rather quickly a kinesthetic response, as in 'muscle memory'.
This training induced learned motion and _coarse_ sighting of ones arm be it a handgun, longgun, knife, or bow too results in correct and very accurate placement of specifically the firearm as within the area of the threat.
Further non gun sight specific cues are very much available as well including sighting by way of simply 'pointing' the firearm at the target. Or using the back of the firearm as a large 'sight' of sorts itself toward aiming at the target which almost always is much larger in total area than that of the gun as viewed from the rear (slide).
Additionally there is simply making a fist, or with with two hands the point of a triangle, to aim the gun at the targets area. This alone can be done with good accuracy under stress against targets as small a 6" childrens plate.
In fact without sights at all persons have been and are very much able to score hits regardless of background illumination and do so not even raising the gun to within their frontal or peripheral vision as below the face.
See indexed point shooting instruction including the featured video of police trainees doing just this; Swedish Police Point Shooting
During the 2008 IDPA Indoor Nationals there was a stage called 'At The Disco' which duplicated _exactly_ what you describe.
It was running of The Standards only it was done indoors inside a testing tunnel with lights turned off but that of a single illuminated as _green_ disco ball.
I shot that year using a gun that had not night sights but OEM target sights front and rear. Both being black.
I shot that stage the best of any stage I'd shot and I shot it better than half the field in my group. So well in fact that national champion and S&W factory shooter Craig Buckland who was working that stage totalled up my points then asked me what sights I was using. When I told him plain target sights he looked puzzled. I then explained telling him this...
At the farthest distances I used my front sight to obscure light from the rear sight as shown forward. When there was no more light to be seen as through the rear sight picture, I then pressed the trigger.
At the closest distance though which was IIRC 15' I simply point shot that stage using the back and top of my slide in to the A/0 zone.
Nothing fancy or gimmicky. Just plain old adaptation as on the fly.
Adapt and overcome...As all I needed to see was what I could see.
Task order was to hit the target. Period. I did not have to hit head only or eyes only. Just the target and not miss the target (drop rounds).
Another person in a different post asked about having shot and trained under low light and adverse light conditions.
I have done just that in training and when using Simunitions (FoF) as using both a handgun (Sims) and with longguns in training, successfully.
This is not difficult to do IF and when one has a primary key item in the form of lighting.
If the subject is dark and you are backlit thus making it difficult to see your sights as in the dark, then that is when and why shooter managed lighting is necessary.
Having clear and highly visible sights without specific ability to _see_ your target and identify it is exactly what results in incidents such as this; Man Shoots Fiancee Day Before Wedding
In fact tonight, by pure ironic chance alone, I went to a MA hunter education instructors seminar as hosted by the state.
During the seminar the subject of sights came out as related to teaching students about same. Be it longgun or handgun as both types of hunting arm are lawful in MA.
The states Administrator was hosting the event and she went on to talk about being able to identify the intended target as "nose to tail", before taking the shot. And how this as a shooters practice greatly reduces chances of hitting wrong game (i.e. antlerless deer) or worst sniping someones cow, dog, or a human being. All of which do unfortunately occur. Hunting goes on from sun up to sundown.
Guess what is key there as well? Light. Light as in being able to _see_ your target clearly as against that of your sights.
Now I'm not saying night sights are not useful.
But outside of narrow situations to which most often the average civilian who is not a police sharp shooter will not occur, standard sights with a light source in hand to positively identify the target are better than night sights with no other means to actually see the target.
This has been tested as well by many folks including Ayoob and sadly to less than desired results by numerous citizens; Tactical-Life.com A Shot In The Dark!
IMHO night sights fall a distant third i pecking order.
Train to a degree that being able to by muscle memory/kinesthetics alone will result in ability to use _coarse_ firing to hit an 8" plate at 15'. This and closer is what is most typcial in max distance that the vast majority of police do encounter combatants as with gun fire. So say the DOJ and FBI. Civilians are same and even closer down to zero feet. You don't need night sights to see a guy standing directly in front of you at arms length or less.
Oppositely civilians are very rarely ever justified to take distant shots at such a distance that fine, rather than coarse, sight control is necessary so as to either hit the target at all (!) and/or situations where fine degree hits are necessary and justifiable. Such as head shots again at beyond 15' or hitting a shooter who is deeply behind bullet resistant cover.
2) Artificial light source
AKA a flashlight.
You should not be firing on what you cannot verify which you cannot _confirm_ as being a threat.
See the dead fiance story. Or see the very many others of same and similar that occur seemingly every 2or 3 months.
3) Night sights
After the above the use of night sights does make sense.
Albeit their actual use in the real world for the vast majority of shootings, and thus 'shooters', is real world narrow be they civilian or police.
Personally 2 of my 3 carry guns have night sights.
The odd one out has a FO front sight with non-illuminated target rear.
Night sights in darkness
Source - http://img520.imageshack.us/img520/8384/sig2wd6.jpg
Darkness illuminated by artificial light
Source - http://img33.imageshack.us/img33/1069/nightsights.jpg
Which 'sight picture' would you rather have AND if you did shoot try to justify/defend (!) as to a jury of your peers?
To me the choice is quite obvious and clear.
Green dots against darkness and shadow I cannot actually 'see' is functionally useless, and quite difficult to defend as being justified.
Light and thus being able to see your target/threat FTW.