( CNN ) -- Prosecutor Gerrie Nel went on the attack again Thursday , trying to discredit a defense witness for Oscar Pistorius on the last day of testimony before the court takes a two-and-a-half week break . Forensics expert Roger Dixon , on the stand for a third day , was grilled over his interpretation of a reconstruction of the scene where double-amputee runner Pistorius killed girlfriend Reeva Steenkamp in February last year . One key line of questioning dealt with the position of a magazine rack within the toilet room where she was shot . Under pressure from Nel , Dixon directly contradicted Pistorius ' version of where he saw the magazine rack when he entered the toilet room after shooting Steenkamp . In his own testimony , Pistorius said that when Steenkamp was slumped over the toilet bowl , she was n't on top of the magazine rack . He said it was off to the side . Nel then showed him a photo of the toilet with the magazine rack standing in a pool of blood -- and Pistorius said it must have been placed there . Dixon directly contradicted this in his testimony Thursday , saying the rack was moved after it was in the pool of blood . The question is important in part because Pistorius contends that police contaminated the crime scene by moving certain key items , including the magazine rack . Pistorius also told the court he opened fire after hearing the sound of movement within the toilet room , which made him believe the door was opening . In retrospect , he concluded that what he heard was the magazine rack moving . In his questioning Thursday , Nel also tried to cast doubt on Dixon 's analysis of a mark on the toilet door that the expert says was made by Pistorius kicking it with his prosthesis , and about the expert 's ballistics reconstruction . Bullet ricochet . Nel 's aim in the murder trial is to prove that Pistorius intentionally shot and killed Steenkamp after a heated argument in the early hours of Valentine 's Day last year . The defense team is seeking to cast doubt on that account and prove that the star sprinter shot his girlfriend through the closed toilet door after mistaking her for an intruder . In his testimony Wednesday , Dixon disputed a conclusion by a pathologist on the cause of Steenkamp 's back wounds . The pathologist said they were made by a bullet ricochet , while Dixon said they were made by the magazine rack . The autopsy said they were made by a blunt , hard object . Following Dixon 's testimony , the court in Pretoria , South Africa , was adjourned until May 5 . When the court reconvenes , the next defense witness will be Johan Stander , manager of the Silver Woods Estate where Pistorius lived and the first person the athlete called after he shot Steenkamp . Gripping trial . The trial is scheduled to continue until the middle of May . Judge Thokozile Masipa will decide the verdict in collaboration with two experts called assessors . South Africa does not have jury trials . If Pistorius is found guilty of premeditated murder , he faces 25 years to life in prison . The trial has gripped South Africa and sports fans worldwide who considered Pistorius a symbol of triumph over physical adversity . His disabled lower legs were amputated when he was a baby , but he went on to achieve global fame as the `` Blade Runner , '' winning numerous Paralympic gold medals on the carbon-fiber blades fitted to his prostheses . He also competed against able-bodied runners at the Olympics . Only those in the courtroom saw Pistorius on the stand , because he chose not to testify on camera . His testimony could be heard in an audio feed . INTERACTIVE : Oscar Pistorius on trial : Explore each side 's case .
Prosecutor Gerrie Nel seeks to discredit expert defense witness Roger Dixon . On the stand , Dixon contradicts Oscar Pistorius ' testimony over position of magazine rack . The prosecution says Pistorius intentionally shot and killed Reeva Steenkamp after a fight . Pistorius denies murder , saying he mistook his girlfriend for an intruder .