JOHANNESBURG — Even if Oscar Pistorius is acquitted of murder, firearms and legal experts in South Africa believe that, by his own account, the star athlete violated basic gun-handling regulations and exposed himself to a homicide charge by shooting into a closed door without knowing who was behind it.

Particularly jarring for firearms instructors and legal experts is that Pistorius testified that he shot at a closed toilet door, fearing but not knowing for certain that a nighttime intruder was on the other side. Instead of an intruder, Pistorius’ girlfriend Reeva Steenkamp was in the toilet cubicle. Struck by three of four shots that Pistorius fired from a 9 mm pistol, she died within minutes. Prosecutors charged Pistorius with premeditated murder, saying the shooting followed an argument between the two. Pistorius said it was an accident.

South Africa has stringent laws regulating the use of lethal force for self-protection. In order to get a permit to own a firearm, applicants must not only know those rules but must demonstrate proficiency with the weapon and knowledge of its safe handling, making it far tougher to legally own a gun in South Africa than many other countries where a mere background check suffices.

Pistorius took such a competency test for his 9 mm pistol and passed it, according to the South African Police Service’s National Firearms Center. Pistorius’ license for the 9 mm pistol was issued in September 2010. The Olympic athlete and Paralympic medalist should have known that firing blindly, instead of at a clearly identified target, violates basic gun-handling rules, firearms and legal experts said.

“You can’t shoot through a closed door,” said Andre Pretorius, president of the Professional Firearm Trainers Council, a regulatory body for South African firearms instructors. “People who own guns and have been through the training, they know that shooting through a door is not going to go through South African law as an accident.”

“There is no situation in South Africa that allows a person to shoot at a threat that is not identified,” Pretorius added. “Firing multiple shots, it makes it that much worse. …It could have been a minor — a 15-year-old kid, a 12-year-old kid — breaking in to get food.”

The Pistorius family, through Arnold Pistorius, uncle of the runner, has said it is confident that the evidence will prove that Steenkamp’s death in the predawn hours of Feb. 14 was “a terrible and tragic accident.”