* State says trial judge misapplied law on dolus eventualis
* Defense says trial judge made no errors in law
* Supreme court to issue verdict within weeks
By Stella Mapenzauswa
BLOEMFONTEIN, Nov 4 (Reuters) - That South African Olympic and Paralympic athlete Oscar Pistorius killed his girlfriend Reeva Steenkamp when he fired four shots through a locked toilet in his home is beyond doubt.
But whether he will be heading back to jail for a long spell or enjoying the relative comfort of house arrest will depend on how the Supreme Court of Appeal interprets the legal principle known by the Latin words "dolus eventualis".
It refers to whether a person foresees the possibility that his or her action will cause death but carries on regardless. It was the crucial element in High Court Judge Thokozile Masipa's decision in the orginal trial to convict Pistorius of culpable homicide instead of the more serious offence of murder.
The previously arcane phrase - which means "eventual fraud" - became ubiquitous during the seven-month trial, from conversations to news columns. When the state opened its appeal on Tuesday seeking to change the conviction to murder, one media commentator even called it "Dolus Eventualis Day".
Judge Masipa said prosecutors had failed to prove Pistorius intended to kill Steenkamp, a law graduate turned model, when he fired through the toilet door at his house in an upmarket suburb of Pretoria in the early hours of Valentine's Day, 2013.
Pistorius had argued that he thought an intruder was in the toilet and that he assumed his girlfriend was safely in bed and out of firing range, a version the state has rejected.
"The submission we made is that there was foresight, that (when) a person (is) standing behind a door in a small cubicle, if you fire four shots into that, a person will die," prosecutor Gerrie Nel told the Supreme Court, opening the challenge on Tuesday.
The prison service released Pistorius on parole last month after he had served about a year of a five-year sentence for culpable homicide, the equivalent of manslaughter.
Legal analysts say the Supreme Court could convict Pistorius of murder itself, which has a minimum 15-year sentence, order a retrial or throw out the state's appeal.
The working definition of dolus eventualis in South African law, taken from the 1963 case of State vs. Malinga, suggests that the intent could apply equally with regard to the intruder Pistorius says he believed was behind the door.
Pistorius was not present at the Supreme Court hearing, a stark contrast with last year's sensational trial during which the track star frequently sobbed uncontrollably as graphic details of Steenkamp's death emerged.
The shooting and trial marked a sensational fall from grace for Pistorius, whose lower legs were amputated when he was a baby but who went on to become a global sporting hero, dubbed "Blade Runner" because of the prosthetic blades he used to compete.
"This will be a trend-setting case, it will definitely be precedent," said advocate Inez Bezuidenhout, director of the University of the Free State's law clinic.
During a terse exchange on Tuesday, Appeal's Court Justice Eric Leach told Pistorius' lead defence counsel Barry Roux he believed Masipa's analysis of dolus eventualis "seems to be wrong".
Roux, in turn, insisted Masipa had not made any errors in law, but "may or may not have committed factual errors."
Some legal experts are worried that the verdict by Judge Masipa could set a bad legal precedent in a country with one of the highest crime rates in the world.
"Had the judgement by Judge Masipa stood, that would have had a detrimental impact in my view on the criminal justice system," legal analyst Brenda Wardle said.
The Supreme Court of Appeal is expected to rule before the end of the year. (Editing by James Macharia and Angus MacSwan)