Pretoria , South Africa ( CNN ) -- The prosecution and defense have made their cases , and now Judge Thokozile Masipa must decide : Did Oscar Pistorius intentionally kill his girlfriend Reeva Steenkamp ? Was it murder ? The verdict is expected September 11 . The judge has to answer several questions to reach her verdict on the murder charge , one of four charges Pistorius faces . First -- and most important -- did Pistorius know Steenkamp was behind the door in his bathroom when he fired four shots through it on Valentine 's Day last year , killing her ? If the answer is yes , beyond a reasonable doubt , Pistorius knew he was shooting at his girlfriend , then the judge will find him guilty of murder . Later , she 'll have to decide whether it was premeditated . If she thinks it was , he could be sentenced to life in prison . In South Africa that means he 'll have to serve at least 25 years . If she thinks the murder was n't premeditated , Pistorius could get a minimum of 15 years behind bars . But if Masipa is not convinced that Pistorius knew Steenkamp was behind the door -- if there is any reasonable doubt of that -- he will not be convicted of murder . Pistorius argues he made a mistake -- that he thought was trying to defend himself from an intruder . If Masipa accepts that as plausible , she will then have to decide if his mistake and his actions were reasonable . If she says they were not , she 'll find him guilty of a crime called culpable homicide . There is no minimum sentence for culpable homicide in South African law -- Masipa will decide the punishment herself , taking South African precedent into account . And there 's one final possibility . If the judge does not think the prosecution has proved its case -- if she believes there is a reasonable chance Pistorius made a reasonable mistake and responded reasonably -- she will find him not guilty , and Oscar Pistorius could be a free man . Masipa will make her decision with the assistance of two experts known as assessors . South Africa does not have jury trials . Lesser charges . Pistorius faces three other weapons charges in addition to the murder accusation . Two charges are related to allegations that he recklessly fired a gun in public -- once in a restaurant in 2012 , and once out of the sunroof of a car in 2013 . Pistorius denies both . The maximum penalty for each charge is five years behind bars . If he is convicted of either , he could face a lesser sentence , such as a fine or the loss of his gun license . The final charge is that Pistorius was found to have ammunition without a proper license when police searched his home after he killed Steenkamp . Pistorius says he was storing the ammunition in his safe for his father . The charge is potentially a very serious one . If he is found guilty , he could face up to 15 years in prison , though Masipa could opt for a lesser punishment such as a fine or the loss of his gun license . Oscar Pistorius trial closing arguments end . Who was Reeva Steenkamp ? Who is 'Blade Runner ' Oscar Pistorius ? CNN 's Robyn Curnow contributed to this report .
Judge Thokozile Masipa must answer several questions to determine her ruling . If Pistorius knew he was shooting at Reeva Steenkamp , he committed murder . Comment: The sentence could be anything up to 25 years , depending on the verdict .