Testifying on day 11 of the trial, firearms instructor Sean Rens read out a gun license test passed by the track athlete, who shot dead Steenkamp through a locked toilet door at his Pretoria home on Valentine's Day last year.
One of the questions asked whether a home-owner was allowed to open fire on burglars on the other side of a security gate.
Pistorius answered: "No", Rens, who taught Pistorius gun safety and sold him weapons, told the court.
Asked in the test about the legal basis for using lethal force, Pistorius answered: "The attack must be against you, a person and be unlawful." In answer to another scenario, Pistorius replied: "No, life is not in danger."
Pistorius also made clear that a gun-owner should never shoot unless he was knew what he was shooting at, and what lay behind the target: "Know your target and what lies beyond," Rens said, quoting Pistorius' answer.
The Paralympic gold medalist, known as the "Blade Runner" on account of his carbon-fiber prostheses, denies the murder charge, saying he shot Steenkamp in a tragic accident after mistaking her, through the door, for a night-time intruder.
Rens also told the court of an incident, related to him by Pistorius, in which the athlete heard noises in his house and went into "code-red or combat mode" only to find the source of the disturbance was a washing machine.
At the time, Pistorius joked on his Twitter account of having gone into "full attack recon mode in the pantry" after thinking an intruder was in his home.
Rens also testified that Pistorius had ordered seven firearms - including an assault rifle and a Smith and Wesson 500 revolver, one of the world's most powerful handguns - although the orders were cancelled shortly after Steenkamp's death.
The testimony is likely to back the prosecution's attempts to depict Pistorius as a gun-obsessed hot-head.
Pistorius' lower legs were amputated as a baby but he overcame the disability to become the "fastest man on no legs", running on artificial limbs to win gold medals at the Beijing and London Paralympics. He also reached the 400 meters semi-finals at the London Games, competing against able-bodied athletes.
If found guilty of murder, he faces at least 25 years behind bars.
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