It's never made clear why this group of scientists need such security as to work in a vault 1500 feet below ground, but they all have a sense of self importance, making themselves and their work irreplaceable. As scientists they are comfortable thinking in terms of data, facts, measurements. They correctly conclude the oxygen will run out before they can be rescued. Their dependence on probabilities leads them to conclude the odds of surviving improve if one dies now. They again depend on probabilities that most of them will not have to kill anyone, and that they will not die. There is no overt decision that any individual should live because of spouse or family. Their only moral value is individual survival.. But they ignore the obvious fact that the largest man will use the most oxygen and should be the one to die- of course that's one of the scientists. Then there is the gun, properly of the security guard. If there was no gun-why is one needed 1500 feet below ground in a locked vault?-its unlikely anyone would have been killed. That bunch would not have worked together to beat one man to death. But this is the USA, don't go anywhere without your gun.
The trial scenes are worthy of Reginald Rose, with Robert Webber as a very aggressive DA, and Frank Overton equally passionate as the defense attorney. You can see why Gene Roddenberry developed a series starring Frank as a defense attorney. Those two actors and Andrew Duggan and Arthur Kennedy dominate the show. Frank Overton had worked with all three in other shows, and likely that strengthened their scenes. There was an unexpected confession at the end, but nonverbal cues suggest even that was not fully truthful. As the defense attorney asked the jury-how would you feel, what would you do?