PRETORIA, South Africa (AP) — Oscar Pistorius’ lawyers tried to roll back the prosecution’s momentum at his murder trial Wednesday following the star athlete’s shaky testimony, presenting a forensic expert who quickly found his own credentials and findings sharply questioned.

With Pistorius now back watching the proceedings from a wooden bench, the double-amputee Olympian’s defense team was attempting to bolster his account that he shot girlfriend Reeva Steenkamp by mistake through a toilet door in his home, thinking she was a dangerous intruder about to attack him in the night. Pistorius faces 25 years to life in prison if convicted of premeditated murder in Steenkamp’s death in the early hours of Valentine’s Day last year.