Prosecutor Gerrie Nel seeks to discredit expert defense witness Roger Dixon . The prosecution has also sought to undermine the credibility of a second expert, Professor David Lewis, who is expected to testify that Pistorius was not responsible for Reeva's death. 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 . The prosecution says Pistorius intentionally shot and killed Reeva Steenkamp after a fight . Pistorius denies murder , saying he mistook his girlfriend for an intruder .
Prosecutor Gerrie Nel seeks to discredit expert defense witness Roger Dixon . The prosecution has also sought to undermine the credibility of a second expert, Professor David Lewis, who is expected to testify that Pistorius was not responsible for Reeva's death. The prosecution says Pistorius intentionally shot and killed Reeva Steenkamp after a fight . Pistorius denies murder , saying he mistook his girlfriend for an intruder .