Pistorius is not claiming self-defense; he is claiming to have been mistaken about his need for self-defense. He is denying that he intentionally unlawfully killed Steenkamp.
Grant said the defense boiled down to Pistorius saying "I made a mistake."
If the court were to rule that the mistake was unreasonable -- based on what an objective, ordinary South African would do in the circumstances of the accused -- he would be found guilty of culpable homicide.
Grant said he would expect a court to probably conclude that it is unreasonable to fire at anybody through a closed door regardless of whether they were an intruder, because of the value of human life.
"I'm expecting that if he beats the murder charge, he is in very grave jeopardy of being convicted of culpable homicide," he said.
What would the sentence be if Pistorius were convicted of the lesser charge of culpable homicide?
If Pistorius is convicted of culpable homicide, no minimum sentencing legislation would be triggered. "Courts are able to exercise their complete and ordinary discretion," Grant said.
This means, theoretically, Pistorius could get a non-custodial sentence if convicted of culpable homicide. Grant said there had been examples of people killing a loved one accidentally where they had avoided jail.
If, however, the court took a view that Pistorius had been grossly negligent, Grant said, he would guess the runner could be jailed for up 15 years.
What impact will the charge of attempted murder faced by the former chief investigator in the Pistorius case have on the Olympian's trial?
Grant said the charges against investigator Hilton Botha would have little if any impact on the Pistorius case, bearing in mind that in countries around the world, the testimony of convicted persons is used against fellow inmates.
"The defense would need to undermine his credibility as a witness, and I don't see how this shows that he is an untrustworthy witness," he said.
"The charges do not, in my view, undermine the credibility of the investigating officer as an honest witness relating to what he discovered at the Pistorius home. If the officer faced charges or had been convicted of crimes of dishonesty, that may well be a different matter."
Would Pistorius be given special treatment in prison if he was convicted and jailed?
CNN's team in Johannesburg understands the double amputee would not receive special treatment, with even blind prisoners being placed with sighted prisoners in South Africa.
But, ahead of his release on bail, the African National Congress Women's League said the athlete was already getting special privileges, adding that his family could visit him outside visiting hours, unlike relatives of other inmates.
"If Pistorius is denied bail, he must be moved to a proper prison facility with others accused of similar crimes," it said in a statement.
"A strong message must be sent out that wealth and celebrity cannot give you an advantage over the law."
What is the reputation of South Africa's legal system?
Grant said that South Africa was proud of its constitution and had a well-respected judiciary and that its substantive criminal law was "similarly advanced and progressive and very well considered."
"The problems that we're facing are more of a systemic procedural nature.
"We have an incredibly strained police force that's not particularly well-trained -- they're massively overloaded -- and we're struggling with issues of corruption within the police force and possibly even within the prosecution service," he said.
Grant said that, regrettably, wealthier South Africans had access to better legal resources than most of their compatriots.
"Unfortunately, most South Africans don't have that extent of resources available to them. They wouldn't have available to them the best possible defense lawyers, but in a strange sense, this is not a problem unique to South Africa. Money buys for you a degree of protection. That's of course a universal problem."
In March, the South African government's midterm report noted that "The effectiveness and ability of the criminal justice system to serve as a deterrent against crime is unfortunately still under threat of being undermined by the actions of a small number of those who serve in it."