The trial of Oscar Pistorius, accused of killing his former girlfriend Reeva Steenkamp, was postponed until April 7 because one of two assessors was hospitalized. 

The assessors will help the judge decide the verdict. South Africa does not have jury trials. 

Pistorius killed Steenkamp on Valentine's Day last year. Of that, there is no doubt. 

But was it murder? 

One of South Africa's toughest prosecutors, Gerrie Nel, has been fighting for most of this month to prove it was. 

On Friday, one of the country's shrewdest defense lawyers, Barry Roux, was scheduled to begin convincing a judge that it wasn't. 

Now he will have to wait. 

The verdict will hinge on two questions: 

Did the Olympic sprinter know his girlfriend was behind the door in the bathroom of his house when he fired four hollow-point bullets through it in the middle of the night? 

And if he did not -- if he thought she was a burglar, as he insists -- did he act as a reasonable person would have? 

Critical testimony will come from the only living person who was in the house at the time, the "Blade Runner" himself. 

Pistorius was expected to take the stand for the first time Friday to give his side of a story he's been telling for more than a year. 

He woke up in the middle of the night, went to his balcony to bring in a fan -- or two fans, in his most recent version -- heard his bathroom window opening, took his gun, went to the bathroom and fired through the door when he heard a noise in the toilet. 
Who is on trial?
The trial of Oscar Pistorius