Pretoria - The State has spent Tuesday morning arguing about whether murder-accused Oscar Pistorius's neighbours heard the screams of a man or a woman the night Reeva Steenkamp was shot and killed.
On Monday, defence witness Ivan Lin, an electrical engineer who specialises in acoustic consultation, took the stand at the North Gauteng High Court.
Lin was asked to determine the difference between male and female screams from different distances.
Some of Pistorius's neighbours told the court during their testimony they heard the sound of a woman screaming on the night of the shooting.
But Pistorius's defence team have argued that the sounds neighbours heard were actually the athlete himself in a state of extreme agitation.
On Monday, Lin said there were no studies that suggested all female or male voices sounded the same.
He said that perception isn't always accurately reflective of the original event, and numerous psychological factors could come into play when hearing such a traumatic set of sounds.
The engineer said he had examined how the closed barriers, such as the bathroom window, the balcony and cubicle doors, and even meteorological or weather conditions could have affected sound.
Lin said that from about 80m away on a balcony, an audible, maybe even intelligible sound could be heard from inside the toilet cubicle.
He did say however, that because some of the neighbours were more than 170m away, they would have been unlikely to hear the noises coming from the cubicle.
It would also be difficult to determine the emotion or gender of these screams from such a distance.
On Tuesday morning, prosecutor Gerrie Nel tried to poke holes in Lin's testimony by asking about the expert's work processes.
He said that Lin's report indicated the exact sound conditions of the night of the shooting could not be replicated.
Lin told the court he had only conducted his experiments in the past two weeks, and had visited Pistorius's former home - the scene of the shooting - to conduct them.
Nel said that since Steenkamp's death last year, the housing estate had changed significantly, with numerous building developments.
“Trees have grown, new houses were built, did somebody tell you about that?” asked Nel.
Lin said that he was aware of these changes and was accompanied by a member of the defence team when he checked the acoustic environment of the estate.
When performing these tests, Lin did admit he wasn't aware the window of the bathroom where Steenkamp was shot was wide open at the time the night of the shooting.
Nel said that this meant that the analysis Lin had conducted where he tested the sound levels when the window was closed had to be discounted.
Nel then argued that each and every day we perceive the differences between male and female voices, and asked if more often than not, we were right.
Lin said that it was impossible to be absolutely certain of the gender of a voice, but conceded the point.
Nel said that the State's version was that Steenkamp had screamed for her life, meaning her screams would be louder than most. He asked if this sound could go as high as 120 decibels.
Lin said that this level of sound could rival a plane taking off, but that it could be possible for a human voice to reach this.
Nel argued that if Steenkamp produced a scream at this level, it could still be intelligible to the neighbours who were 170m away.
The engineer believed it would possibly be intelligible - in other words able to perceive information from the sound - but this was still unlikely.
Lin was then quizzed on the four gunshots and how loud they would be.
Nel said that the State's own sound expert said a 9mm gunshot would create 160 decibels of sound, but Lin said he had not conducted his own tests using gunshots.
Nel asked about whether a woman's voice would have a particular tonal character, and Lin confirmed this was the case. However, he would not confirm whether a woman's voice would therefore be more audible.
The expert said Nel was trying to use a standard of analysis which applies to normal, lengthier sound scenarios. Lin said he was convinced that his analysis - that the neighbours further away most likely wouldn't have heard Steenkamp's alleged screams - was still correct.
He did concede, however, that he had not made a finding on a person's ability to differentiate between a male and female scream.
Nel said that all four of the neighbours who have been called as State witnesses had believed they heard a woman screaming that night.
Lin admitted that he had not excluded the possibility that the neighbours could differentiate between a male or female voice from their respective distances.
In his re-examination, defence advocate Barry Roux asked for a demonstration to determine the ambient noises inside the courtroom.
The trial continues.