Forensic geologist and university lecturer Roger Dixon addressed the court in Pretoria on Wednesday, contradicting evidence from the prosecution that there was a short break between the first and second shots fired at Reeva Steenkamp.
Mr Dixon asserted that Ms Steenkamp was shot in quick succession in the hip and arm as she stood close to the edge of the bathroom door.
Prosecutor Gerrie Nel described Mr Dixon as "irresponsible" for going against what a police ballistics witness and pathologist have asserted in relation to the sequence of shots.
And Mr Nel continued his cross-examination of Mr Dixon on Thursday, quizzing him on a light test carried out in Pistorius' bedroom.
Mr Dixon also told the court about sound tests of a cricket bat striking a door and bullets hitting a door.
Before the start of Thursday's proceedings judge Thokozile Masipa warned those watching televised proceedings in an overflow court about their behaviour, said to include shouting, cheering and booing.
"It is not an entertainment place,'' she said.
Olympic and Paralympic athlete Pistorius is charged with the "wilful and intentional murder" of Ms Steenkamp after shooting her dead at his home in Pretoria on February 14, 2013.
Pistorius has always maintained that he did not intend to kill his then girlfriend, insisting that he mistook Ms Steenkamp for an intruder.
The trial has now been adjourned and will resume on May 5.