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The Stipps vs The Nhlengethwas

There is a common perception that the Nhlengethwas – whose bedroom window was only 25 metres away from the toilet and bathroom windows – were in the best position to hear and to interpret the screams that came from Oscar’s house. To believe this is a mistake. There is no evidence to support this.

A large part of our book is dedicated to analyzing the acoustic evidence in order to, among others, answer the following two questions:

  1. Who would have heard the screams emanating from the toilet or bathroom the best, i.e the loudest and the clearest? The Nhlengethwas or the Stipps?
  2. Could the Nhlengethwas have been wrong in that they confused a woman’s screams for a man’s crying?

In our analysis we took the following into account:

  • The Stipps slept with both their balcony doors open. The Nhlengethwas’ bedroom windows were closed and covered with horizontal wooden blinds – closed so tightly that no outside light could get in.
  • The Stipps listened to the screams while standing outside on their balconies facing the direction of Oscar’s house. The Nhlengethwas heard the screams/cries only within the closed confines of their bedroom and only after they pulled the blinds aside to look what was going on outside.
  • The Stipps had a perpendicular unobstructed line of sight to the toilet and bathroom windows. The Nhlengethwas had a very oblique line of sight (about 70 degrees to the perpendicular) to the toilet window that was partially obstructed by a balcony.
  • To reach the Stipps the sounds of Reeva screaming in the toilet had to travel through one closed window and then a distance of 72 meters. To reach the Nhlengethwas the screams had to travel 25 meters through two closed windows (one of which was covered with closed wooden blinds).

In the book you’ll see the results of our research, analysis and sound mapping that lead to the following conclusions:

  • Irrespective of who screamed the Stipps would have heard the screams at least three times louder than the Nhlengethwas.
  • The frequency distribution of the acoustic profile of the scream that the Nhlengethwas heard would have been significantly more “modified” than what the Stipps were exposed to. In essence a typically high pitch female scream would have sounded less like a female scream to the Nhlengethwas than to the Stipps.
  • Even Mr Johnson would have heard the screams louder and clearer than the Nhlengethwas.

In addition one must also consider that:

  • The Stipps’ testimonies that they heard a woman scream before the “second sounds” at about 03:17 is conclusively corroborated by the testimonies of Mr Johnson and Mrs Burger.
  • Mrs Motshuane does not conclusively corroborate the Nhlengethwas’ testimony. In our book we elaborate more on why we say this.
  • Mrs Van der Merwe didn’t hear the same screams that the Nhlengethwas testified they heard. Read more here.

This leads us to the most likely scenario:

  • If a mistake was made in the identification of the screaming then that mistake was much more likely made by the Nhlengethwas and not the Stipps.

Why then did the court side with the Nhlengethwas?

The sins of Roger Dixon

Roger Dixon – who can forget his stellar performance as a paid defence expert in the Pistorius case? One just has to search for #rogerdixon in Twitter to get an idea of what the public thought of his conduct in court. For example:“We should have a new scale for rating disasters. 1 to Dixon. Where 1 is fairly bad and #Dixon is earth-shatteringly abysmally dreadful.”

When State prosecutor Advocate Gerrie Nel said that Roger Dixon was the worst witness that he had ever experienced in court he had good reason to say so. Roger Dixon thinks it is quite acceptable to testify under oath in areas that he admitted he is not qualified in, such as for example pathology and ballistics. He didn’t produce any written documents and reports describing his studies, methodologies, assumptions, equipment, results, conclusions, limitations, etc. For example, Dixon was tasked to observe the light conditions in Pistorius’ house. Dixon did some of the observations on a night when the moon was full, while on the night of the shooting it was new moon and much darker.

Another example is when he was asked to study what Dr Stipp would have seen of Oscar through the open bathroom window that night. So what did Dixon do? One night he stood outside the Stipp house in the street – to observe a person standing on his knees inside the bathroom in front of the open window. It turns out the person on his knees was about 20 cm shorter than Oscar on his stumps – and while Dixon did his observations standing in the street Dr Stipp was standing on the balcony – about three metres higher than Dixon. The problem with this set-up is so obvious hat it doesn’t even need to be explained.

The question on many people’s minds must be – why did the defence employ the services of Roger Dixon?

Perhaps to answer this question we need to look at the Dixon’s involvement in another high profile case in  back 2007 – State vs. Fred van der Vyver – who stood accused of the brutal murder of his girlfriend Inge Lotz.

During a break in the proceedings of the Pistorius trial Roger Dixon made a very insightful comment to a well-known journalist, Debora Patta. He said that he was instrumental in getting the accused in the Inge Lotz murder (i.e. Fred van der Vyver) acquitted.

Let’s see how he accomplished this:

Shortly before the trial started in early 2007 the State approached Senior Superintendent Roger Dixon, at the time a Control Forensic Analyst at the Scientific Analysis Unit of the Forensic Science Laboratory in Pretoria, to examine a fingerprint lift (Folien 1) in order to determine whether it was lifted from a DVD cover or from a drinking glass. If the print was from a DVD cover Fred van der Vyver would be guilty, and if the lift came from a drinking glass the case against Fred van Der Vyver would have been severely weakened.

In late 2006 Roger Dixon conduct various tests on DVD covers and drinking glasses supposedly “collected from Inge’s flat”. Then through a process that “required skills in image analysis and comparison” he compared the lifts with Folien 1 and came to the ultimate conclusion that in his opinion Folien 1 was not lifted from a DVD cover but instead from “one of four glasses found in Inge’s flat”.

Dixon’s conclusion verbatim:

In my opinion the back folien described in paragraph was not ‘lifted from a DVD’ but instead from one of the four glasses described in paragraph 6.4. The features observed on the folien match test lifts made from the glasses, and not those made from the DVD covers.

The black folien Dixon referred to was Folien 1 and the four glasses were those numbered 1, 6, 7 and 8 in the photo below.

Dixon reported his results in a signed affidavit, dated 12 December 2006, in terms of Section 212 of the Criminal Procedure Act 1977 (Act 51 of 1977).

This affidavit compelled the Director of Public Prosecutions to, on 13 December 2006, send a letter to the Advocate Dup de Bruyn, Fred’s lawyer, which said: I hereby confirm that the State no longer intends to proceed with evidence concerning your client’s alleged fingerprint on the DVD holder.

This affidavit was accepted as prima facie evidence by the court. Roger Dixon did not have to testify in court.

Judging from Judge Deon van Zyl’s verdict below Dixon’s affidavit was crucial to the outcome of the case. It dealt the legitimacy of Folien 1 a severe blow.

[140] It follows that the state in no way submitted sufficient evidence to affect the prima facie case, as contained in Senior Supt Dixon’s affidavit in the least. This prima facie case was indeed strengthened considerably by the highly expert presentations of Mr Wertheim and Mr Zeelenberg. ...

 [141] In their comprehensive reports and impressive testimonies, did they affirm and expanded on Senior Superintendent Dixon’s findings in his affidavit point by point.[…] They were both of the opinion that its (Folien 1) came from a comical drinking glass about 80 mm high. …

The problems with Dixon’s affidavit are severe – and renders it completely inadmissible as prima facie in court. The fact that the court accepted it must be seen as a legal error – which could have been used by a willing and competent Director of Public Prosecutions to successfully appeal the verdict of the Criminal Court.

The Section 212 affidavit does not comply with the strict provisions of Section 212 of the Criminal Procedure Act

We had Dixon’s affidavit reviewed by a legal expert with extensive knowledge of Section 212 of the Criminal Procedure Act. These are his words verbatim:

My initial view was that the affidavit could only be used as toilet paper and nothing else. I am still of that view.

One of the most critical shortcomings of the affidavit is that the 11 drinking glasses which he used in his experiment had no chain of custody documentation. In fact, evidence and undisputed court testimony suggest that the 11 drinking glasses were not collected by the police from Inge’s flat. Where these glasses came from is still a mystery to this day. Without proper chain of custody documentation, Dixon could legally not refer to tests conducted on them in his Affidavit.

Roger Dixon’s Section 212 affidavit contains calculated mistakes, omissions and lies

The two “curved” lines on Folien 1 – supposedly made by the top rim and the bottom edge of a conical drinking glass are about 80 mm apart. In other words, if the drinking glass made these lines then the glass had to be 80 mm tall. Fact is that the drinking glass Dixon said made the lines is actually about 83 mm tall. In the photo below observe how Dixon ignored the “gap” between the short edge of the ruler and the zero mark.

In his affidavit, Dixon says that he actually met Const Elton Swartz – the officer that lifted Folien 1 at the crime scene – claiming that Constable Swartz demonstrated to him how Folien 1 was lifted and that he then used the same method in his experiments.

The fact is that the method Dixon used was incorrect – because he never met with Const Elton Swartz. Constable Swartz has never demonstrated anything to Dixon. A clear case of perjury.

These are just but a few examples of the problems with Dixon’s affidavit. Please read an Open Letter to Roger Dixon on our website regarding the Inge Lotz case –

So what picture do we get of Roger Dixon? He seems to be a person that is quite willing to overstep legal boundaries when it suits him. He has no concept of what it means to be an expert witness and what his duties to the court are. The defence saw in him a person that would be a real team player – that would have no qualms to say whatever they needed him to say to support Oscar’s version. He has an over-inflated sense of his own abilities and firmly believes that his opinions – even when not backed up by real scientific research, analysis and investigation – can and should be accepted as solid evidence in court.

Mrs van der Merwe – 1st or 2nd sounds?

The testimony of Mrs Estelle van der Merwe was used by the State in an attempt to prove that there was an argument between Oscar and Reeva before the gunshots. We will deal with the evidence of an argument in a later post.

In this post we deal with the defence’s misguided and dishonest attempt to use Mrs van der Merwe’s testimony to prove that Oscar’s version was true. Throughout the trial the defence made several statements as if they were the undisputed truth, without any objective evidence, just because they fitted Oscar’s version of events. One such statement is that Mrs Estelle van der Merwe heard the “first sounds” and not the “second sounds”.

First some background:

Estelle van der Merwe said she woke up at about 2 am hearing a female voice. She couldn’t hear the words, nor the language, but judging by the “movement” in the tone of the voice she was confident that it came from a woman. It sounded like the woman was arguing with someone – although she couldn’t hear the second voice. The female voice was intermittent, i.e. it was quiet for periods, which could have ranged from 5 to 20 minutes, and lasted for about an hour.

She was irritated by the noises and tried to put a pillow over her head to block out the noise and get some sleep. At some stage she got up to check whether she could see anything. She looked in the opposite direction of Oscar’s house, towards Farm Inn (a small nature reserve close by) but didn’t see anything. She couldn’t tell where the sound was coming from. Then at about 3 am she heard four thuds (“plof geluide”) in rapid succession. These sounds also woke her husband. She asked her husband what these sounds were and he said they were gunshots. He got up and looked out of the window but didn’t see anything out of the ordinary. A while later, after hearing a commotion, Mr van der Merwe called security. After his phone call they heard someone crying very loudly – to her it sounded like a female, and to him it sounded like Oscar.

Around about 03:00 in the morning I heard four gunshots M'Lady. (Record 159, Lines 19–20)

Now let’s look at how the defence dealt with her testimony:

Consider the following statement from the defence’s Heads of Argument:

21. Mrs Van der Merwe’s evidence makes it clear that the first sounds were the gunshots. Mrs Van der Merwe’s evidence is that she heard a female voice far away, which was not constant, thereafter she heard four gunshots and then the screaming.

It was very important to the defence’s case that Mrs van der Merwe heard the “first sounds”. Then the four thuds she heard, and the screaming thereafter fits Oscar’s version well and puts additional doubt on the very damaging testimonies of the Stipps, Burger and Johnson.

The defence’s reasoning as to why Mrs van der Merwe’s testimony “makes it clear” is explained in Par 206 of their Heads of Argument:

206.2 At approximately 03:00 she heard four gunshots (Record 159, lines 19–20), which was confirmed by her husband to have been gunshots (Record 161, lines 9–10). The shots occurred one shortly after the other (Record 161, lines 1–3).

206.3 After the four shots, she heard somebody crying out loud. It appeared to her to be a woman’s voice but her husband told her it was the Accused (Record 161, lines 24–25 and 162, line 1).

206.4 What is clear from Mrs van der Merwe’s evidence is that the crying out loud, which sounded like a woman, was after the first shots.

Forgetting about Oscar version, or anybody else’s testimony – on its own merits, what precisely about Mrs van der Merwe’s testimony makes it clear that she heard the “first sounds”?

206.5 We will demonstrate hereunder that the crying out loud (or screaming) occurred between approximately 03:12 and 03:17.

This is not in dispute.

206.6 It is thus clear that the four shots heard by Mrs van der Merwe occurred prior to 03:12 which is consistent with her statement of “round about 03:00”.

What about the statement “round about 03:00” puts the sounds conclusively before 03:12 and not after at 03:17? “Round about 03:00” is an expression of uncertainty – how can it support a statement like “it is thus clear”?

Hypothetically, how would it go down if a witness testifies – “the accused looks more or less like the person I saw committing the murder?” And the prosecutor argues – “It is thus clear that the accused is the murderer because he looks more or less like the person the witness saw.”

This is precisely what the defence did when they argued that “about three o’clock” could only refer to an event that took place at be 03:12 and not at 03:17.

In spite of the lack of objective evidence the Judge Masipa fell for it – hook, line and sinker: (Page 3301 Lines 10–18)

Ms Van der Merwe woke up around 01:56 to hear a one-sided argument, later heard four gunshots in close succession. Her estimation was that it was about three o’clock. Soon thereafter she heard someone crying out aloud. It seemed to her that it was a woman’s voice, but her husband told her that it was the accused crying. Although it was not established how her husband knew that it was the accused who was crying, this piece of evidence is enough to throw some doubt on the evidence of the witnesses who are adamant that they had heard a woman scream.

The court could only have come to this conclusion if she accepted that Mrs van der Merwe heard the “first sounds”.

In our book Oscar vs The Truth we convincingly show that the Van der Merwe house was so located relative to Oscar’s house, that they would not have been able to hear Reeva scream from a closed toilet, neither would they have been able to hear Oscar scream from the bathroom with an open window. Therefore the screaming they heard sometime after the gunshots did not originate in the bathroom but elsewhere in the house where there were windows facing in the direction of the Van der Merwe house. The only time that Oscar found himself in such a location was after the gunshots when he ran downstairs to open the front door.

If Mrs van der Merwe heard the “first sounds” as the defence argued, and the court accepted, it puts her in conflict with Mrs Stipp – who was awake and alert and in a far superior position to hear any sounds emanating from the Oscar’s bathroom.

It is clear that Mrs van der Merwe rather heard the “second sounds” – the gunshots – and then thereafter the agonizing cries of Oscar as he ran downstairs.

What did Nhlegenthwa hear?

Mr Nhlegenthwa, the immediate neighbour to the right, claimed that he heard Oscar’s high pitch crying prior to his phone call to security at 03:16:15 when he spoke to Mr Pieter Baba to report the loud crying he heard.

When one compare the testimonies of Baba and Nhlegenthwa, in relation to this phone call at 03:16:15, a huge inconsistency jumps out. The question then is – what does this inconsistency mean?

Listen below to the cross-examination of Baba by Advocate Roux.

There was also a call from Mr Nhlengethwa, that is the neighbour of Mr Pistorius and we know that was at three sixteen thirteen and again at three sixteen thirty six. The first one did not go through, but at three sixteen thirty six, it was 44 seconds. --- That is correct, M'Lady.

And that is the call where he also spoke about the gunshots?
--- That is correct, M'Lady. (Record 434, Lines 18–25)

Mr Baba agreed when Advocate Roux put it to him that it was during the first call at 03:16 that Mr Nhlegenthwa told him about the gunshots. No mention of Oscar crying.

Now listen below to Nhlegenthwa’s version:

Then after that, at 03:16:36, there was again a call and that lasted, the duration was 44 seconds. Could you tell the court about that? Who did you … and we know it is a phone, it is a call to security? --- That is correct, M'Lady. At that moment when my call went through, M'Lady, I spoke to the gentleman there at the security gate, of which I informed him that I am staying at number 287. I first told him that I am Michael, I am staying at number 287, can you quickly come up towards my house because I hear there is a man who is crying and I think he is desperate for help, so something might have happened to him. So, but I said to him, I am not sure, but quickly check the neighbours around me. That is what I said to him. (Record 2211, Lines 24–26 & Record 2212, Lines 1–8)

There is no mention whatsoever of telling Mr Baba about gunshots.

Baba’s testimony was on Day 5 (7 March 2014) and Nhlegenthwa’s testimony was two months later on Day 26 (6 May 2014). What happened in these two months between March when Roux admitted that Nhlegenthwa spoke about gunshots and May when Mike Nhlegenthwa supposedly didn’t hear any gunshots but only a male person crying? Could it be that the defence came to realize that it would be absolutely essential to have a witness that heard Oscar’s screaming/crying before the “second sounds”?

Without such testimony there is nothing to prove that Oscar’s cries/screams could not have have been after the “second sounds” – the gunshots – and that the screaming before the “second sounds” could therefore have been those of Reeva – as testified to by the Stipps, Burger and Johnson. We must also keep in mind that  there is actually no other objective evidence that all of the bat strikes came after the four gunshots. (We will deal with this in detail in our book Oscar vs The Truth).

In our book we also convincingly show that even if the Nhlegenthwas did hear someone scream before the “second sounds” that they likely heard Reeva’s screams – that they were actually the ones that made a mistake in identification and not the Stipps, Burger and Johnson.

What did Stander tell Oldwage?

The defence argued that Oscar could not have known that Dr and Mrs Stipp would testify about the first sounds and the seconds sounds. Is this true?

In their Heads of Argument the defence stated:

287. When the Accused deposed to his bail affidavit, he was neither privy to the statements in the police docket nor to the evidence to be led at the bail application. He could not have known that Dr Stipp and Mrs Stipp would testify about the first sounds and the second sounds. This underlines his credibility in this regard.

Judge Masipa concurred:

Counsel for the defence correctly argued that it was highly improbable that the accused would have made this up so quickly and be consistent in his version, even at the bail application before he had access to the police docket and before he was privy to the evidence on behalf of the state at the bail application.

Mr Stander testified that while he and Dr Stipp were talking that evening outside Oscar’s house, he asked him what he had heard. Stipp supposedly told him that he heard four shots, silence, screams and again four shots. Before Stipp left the scene Stander asked him for his phone number in case the police may want to speak to him later.

[Stander] Mr Stipp was with me outside then. Sorry M'Lady, Doctor Stipp. I asked him what happened. If he heard anything, because he was staying ... he said he was staying just behind Oscar. He said to me: He heard four shots, silence, screams and four shots again and then he mentioned to me that he cannot do anything. He is going to leave. I asked him his telephone number to give it to the police if they asked for it. (Record 2144, Lines 19–26)

(It is curious and somewhat suspicious that Stander recalled something very different than what Stipp swore to under oath – three shots, screaming moments later and then three shots.)

We also know that Adv Kenny Oldwage arrived on the scene that night. We also know that Stander and Oldwage talked at some point that morning and that Stipp came up in discussion. At 04:30 Stander called Stipp to inform him that he had passed his phone number to the defence lawyer (i.e. Adv Kenny Oldwage) who would be contacting him.

There is just one other small detail, but you phoned Doctor Stipp later. --- That is correct, M'Lady.

And indicated to him that the defence might be in contact with him? --- That is correct.

You just wanted to check his number. --- That is correct, M'Lady.

Why did you do that? --- In my mind, it is the right thing to do.  if M'Lady, you give your number to me, and I give it to Mr X, then it is good manners and the right thing to do, to inform you saying I gave your number to this person, he will probably phone you.  That is only [intervene].

So when you phone him, you already gave his number to the defence? ---That is correct, yes.

Who did you give the number to? --- I gave it to Advocate Oldwage.

Okay. So when you phoned Mr Stipp earlier that morning, you already gave his number to Mr Oldwage? --- That is correct, yes. (Record 2166, Lines 4–19)

We also know that Oscar didn’t do his own bail affidavit:

M'Lady … when my bail was done, it was done by my legal team. It was read to me in a holding cell. I was on medication. I was traumatised. I read it and it was the truth and I signed it, M'Lady. (Record 1825, Lines 1–4)

It is highly, to extremely, likely that Oldwage was part of the legal team that drafted Oscar’s bail affidavit and indications are that he likely knew about the shots and screaming Dr Stipp heard, prior to his involvement in the bail affidavit. When Stander gave away Dr Stipp’s  phone number it is not unrealistic to assume that Stander also told Oldwage what Dr Stipp told him about the shots and screaming. What are the chances that Oldwage didn’t in turn pass this information on to Oscar?

How loud can a woman scream?

The most critical variable to consider in doing an acoustical analysis of the screams that were heard in the early hours of  14 February 2013 is how loud Reeva could have screamed. Since no one ever measured Reeva screaming under the circumstances that she faced that night we are left to make assumptions about how loud she could have screamed.

The defence’s acoustic expert, Ivan Lin, based all his analyses assuming that Reeva and Oscar would have screamed at a sound level of 110 dBA.

“From my experience and the past researches, typical human screams recorded as between 110 dBA [100dBA] to 120 dBA.  For the purpose of this exercise, I shall use an average value of 110 dBA.” (Page 2643, Lines 6–9) [the 110 dBA is an incorrect recording – Lin actually said 100 dBA]

Read here for more information about sound levels and how they measured.

His assumption that Oscar would have screamed at the same level as Reeva is already problematic given the wealth of evidence that women on average scream substantially louder than men. In addition, a woman locked up in a toilet fearing for her life is unlikely to produce a typical average scream.

Making an assumption about how loud Reeva would have screamed cannot be made lightly or arbitrarily. It may look small on paper, but 10 dBA is a huge difference on the logarithmic decibel scale. A scream at 120 dBA sounds more than twice as loud to the human ear as a scream at 110 dBA.

Let’s do a very simple and easy exercise. Please open Google Search and type in the phrase “how loud can a woman scream”? Within the top three results you will find the following link: (Forensic Analysis of the Audibility of Female Screams by Dr Durand Begault, AES 33rd International Conference, Denver, CO, USA, 2008 June 5–7)

In a controlled soundproof environment Dr Begualt asked ten females to scream as loud as they could, as if they have been surprised by something scary. The maximum sound levels achieved in rank order are: 123, 122, 122, 118, 115, 110, 109, 109, 108 and 102 dBA’s. The three highest screams were all woman below 30 years old. And the sound level decreased with age. The 102 dBA scream was from the oldest participant, and at the time of the test she suffered from an allergy.

Reeva Steenkamp was 29 years old when she died.

What did the acoustic expert say in court? During cross-examination Advocate Gerrie Nel wanted to know if a woman fearing for her life could have put the dB closer to 120 than 110 dB. The expert said that 120 dB is almost the same as a jet engine taking off and that there is only a very slight possibility that she could have screamed at 120 dBA.

[Nel] That is so. If somebody screams in absolute fear, would you not put it closer to 120 than 110?

[Lin] I think if one need to appreciate what 120 means. 120 dB is extremely loud, it is almost hearing a jet taking off at a 100 meter away and that is not ... that is extremely [indistinct] human voice and it is a very slight possibility but it is a possibility.

[Nel] I appreciate what you just said. It is at the extreme limits of a person’s voice.

[Lin] Yes.

Page 4668: Lines 14 to 40.

Compare this “very slight possibility” and “extreme limits” with Begualt’s sample where 30 % of test subjects screamed louder than 120 dBA – and all of them were less than 30 years old.

It is common practice to, when dealing with variables and uncertainties, to perform a sensitivity analysis. This is what the expert did with the ambient (background) noise levels when he assumed a range of 20 dBA to 45 dBA. This while he could have gone out to the Silver Woods Country Estate at night and actually measure the real ambient sound level himself. The question is why didn’t he do a sensitivity analysis with the loudness of a scream? He said that a typical scream is between 100 dBA and 120 dBA. It would have been far more beneficial to the court if he performed a sensitivity analysis with both these different scream sound levels.

What is clear and what our own analysis will show is that any analysis performed with 120 dBA scenario would have been very detrimental to the defence’s case.

What did the court thought of the expert’s analysis and testimony?

In any event, the evidence of Mr Lin, an acoustic engineer, cast serious doubt on whether witnesses who were 80 metres and 177 metres away respectively from the accused’s house would be able to differentiate between a man and a woman’s screams, if the screams were from the toilet with closed windows.

(The Stipp’s were in fact 72 meters away from Oscar’s bathroom window – and not 80 meters as assumed by the expert and accepted by the court.)

We will show that the court’s conclusion above has no scientific merit and that the four state witnesses (Dr Stipp, Mrs Stipp, Mr Johnson and Ms Burger) would have heard Reeva’s scream audibly and intelligibly to the extent that they would have been able to tell the difference between a male and female scream. We will also show that the four state witnesses would have heard Reeva scream louder and clearer (i.e with greater quality, audibility and intelligibility) than the immediate neighbours and if there was a case of mistaken identification then the mistake was much rather made by the defence witnesses (the immediate neigbours) than by the State witnesses.

In closing lets remind ourselves of what the duty of an expert witness is:

“... the value of an expert is not to espouse and further the cause of a particular party, but to assist the Court in coming to a proper decision on technical and scientific matters. It should therefore at all times be remembered that an expert is primarily there to assist the Court and not necessarily to further the cause of his particular client to such an extent that he loses objectivity and in fact undermines his client’s case.”

State vs Huma

Whom did the acoustic expert serve?

Ambient Noise

To analyze the acoustics of this case, in order to determine if the state witnesses would have heard the screams if they came from Oscar’s toilet with a closed window, there are two critical parameters about which assumptions have to be made. These are: 1) How loud would Reeva have screamed, and 2) what were the ambient noise levels within the bedrooms of the witnesses?

Ambient noise is also called “background noise”. It is typically the noise caused by ventilation systems, traffic, refrigerators, etc.

Please read “How loud can a woman scream?” for our argument that the defence’s assumption that Reeva would have screamed at a sound level of 110 dBA was a lazy overly conservative assumption made only to assist Oscar’s version.

This post looks at the second parameter – ambient noise levels.

Ivan Lin, the acoustic engineer employed by the defence to assist Oscar, assumed a range of 20 to 45 dBA for the ambient noise level.

From my experience as I typically measured in a similar quiet luxury housing estates, the [indistinct 14:13] or ambient noise level inside or on a balcony of the listener’s house in the early hours of the morning, would be in a range between 20dba and 45dba. (Page 2653, Lines 20–24)

Note that he does not say that he actually measured the ambient noise level inside this specific estate at about 3 o’clock in the morning. Why didn’t he? We know that the defence was in the Estate on several occasions to conduct tests with people arguing and screaming inside Oscar’s house. It would have been a simple and small task to measure the actual ambient sound levels.

Also note that he did not use a similar range of values for the loudness of a scream. Why use a fixed value of 110 dBA while he could have done his analysis for a realistic range – e.g. 110 to 120 dBA? The answer to this is quite simple: the defence could not allow a 120 dBA scenario to be analyzed as this would have been very detrimental to their case.

The range of 20 to 45 dBA is so large that for all practical purposes it is really of no use to assist the court.

Let’s try and narrow it down a bit.

The defence got their expert to use a professional sound level meter to conduct a number of sound level tests in the court room. Here are a few relevant readings:

  • 40 dBA – Silent court room, packed with people, with recording machines running and and a few people typing,
  • 45 dBA – With Advocate Barry Roux talking.

It should be clear that neither of the two scenarios above are representative of a bedroom (without air condition or fans running) nor a balcony at about 3 am in a sparsely populated residential estate. We can can thus safely conclude that the ambient sound level was less than 40 dBA.

Typical dBA levels within octave bands for different Ambient Noise scenarios

The table above show typical sound levels for different land-use scenarios (derived from source data at Engineering Toolbox). The estate is situated in close proximity to the Farms Inn nature reserve and was at the time relatively sparsely populated. It is therefore not unreasonable to assume that the ambient noise level would have been between 30 and 35 dBA.

Therefore in our acoustical analysis elsewhere on this website we will use a conservative 35 dBA.

As we know, any sound/noise has a frequency spectrum. A frequency spectrum is typically divided into octaves. Each octave has its own sound level. The overall sound level of a noise is determined by combining the sound levels across all the octaves. (Read here how)

The table above also shows the frequency spectrum of typical ambient noise for different land-use scenarios. It is evident that for typical background noise with a sound level of 35 dBA the sound level within the 2000 Hz octave is only 24 dBA. The reason why we emphasize the 2000 Hz octave here is because this is the octave in which a typical female scream has most of its intensity.

The reason why it is important to consider the ambient sound level is because if it is high enough it can “mask” a sound (voice, scream, etc.) and render it inaudible and unintelligible. An important parameter here is the signal-to-noise ratio (SNR). The SNR is the difference between sound level and the ambient noise level.

A minimum SNR of about 6 dBA is required for sound to be audible and intelligible above ambient noise, while 10 dBA to 15 dBA is ideal. However according to McLain (2015), in the majority of real-world listening conditions, people can recognize speech with an SNR that commonly ranges from –10 to +5 dB.

How can a low or negative SNR be audible and intelligible? Consider the illustration below –

When one superimposes the profile of say a scream (in green) over the profile of ambient noise (in red), portions of the scream’s profile will be above the ambient profile, even when the overall ambient sound level may be higher than the overall sound level of the scream. The portion/s of the scream’s profile that is more then about 6 dBA above the ambient profile (green shaded area) will be audible – and this is often sufficient to make the scream/voice  audible – especially when the frequencies that exceed the corresponding ambient levels are those frequencies that the human ear are typically most sensitive to. That is why people can recognize speech in real world listening conditions where the SNR is below zero.

Ultimately it comes down to this: in order to assess the audibility of a scream above the ambient noise levels (especially when SNR values are small or less than zero) one also has to consider the SNR’s within each octave band. The defence’s expert did not do this.

How well did the Stipps hear?

The following conversation occurred during the cross-examination of Dr Stipp.

Roux: What we do know is that she was in the toilet – and the toilet windows were closed – on the State’s version.

Stipp: That’s correct

Roux: And the accused was outside the toilet where we say to you the window was open.
Stipp: That’s correct.

Roux: I can understand he screams, but what I will put to you in the Defence’s case – when someone is in that toilet it is a closed confined space with a closed window and a closed door you would not hear a woman screaming and in any event not so distinct that you will make out emotion ... if she was inside the toilet. (Record 374, lines 14–19)

Here we have the defence putting it to Dr Stipp that it was impossible for him to hear Reeva scream from the toilet, or that in any case he would not have been able to hear the screams so distinct that he would have been able to make out the emotion of the screams.

We put it to Advocate Roux that he didn’t know what he was talking about – even his own acoustic expert Ivan Lin contradicted him later during the trial.

What did the defence’s expert, Ivan Lin, say?

At plus minus 80 metres away, if the sound emanated from the toilet, sub-point: if the listener was on the balcony a scream emanating from the toilet at source, can range from 46 dBA to 48 dBA. Based on the ambient noise levels there at the listener’s location of between 20 dBA and 45 dBA. The sound is in the range of audible and intelligible. (Record 2654, lines 2–7)

Let’s first look at the lay of the land.

Mapdata: Google – DigitalGlobe

The Stipps’ house is 72 meters away from the side of Oscar’s house where the bathroom and toilet windows are situated. (Not 80 metres as incorrectly assumed by the defence’s acoustic expert). There were no buildings in between. There was a direct line of sight from inside the Stipps’ bedroom, as well as from the two balconies.

The window to the Stipp bedroom and the two balconies.

When the Stipps heard the “first sounds” they were inside their bedroom with both balcony doors open to some degree. Moments after the “first sounds” they moved to these balconies to listen to the screaming emanating from Oscar’s house.

The small rectangle to the right in the photo below is the window to the toilet in which Reeva was killed.

View from the Stipp’s bedroom towards Oscar’s house.

Sometime around 3 am Mrs Stipp woke up – she was feeling a bit ill. She stayed in bed as she pondered on whether to get up for a drink of water or not. When she finally decided to get up for a drink of water she heard three sounds that sounded to her like gunshots. These sounds also woke up her husband, Dr Stipp.

“Moments” after hearing the “first sounds” both Mrs and Dr Stipp moved to the balconies. While standing on the balconies they listened to the screams. They weren’t sure where the screams came from. They saw that the light in Oscar’s bathroom was on. Dr Stipp saw someone with a fair complexion walk in the bathroom from right to left. Mrs Stipp testified that she is absolutely convinced it was a woman’s screams she heard – judging by the pitch and tonal character of the scream. Shortly before the “second sounds” she also heard a man’s voice occurring at the same time as the screams. She even remarked to her husband that she was hearing a man’s voice.

The defence retained Ivan Lin, an acoustic expert, to answer the following question: Could the State witnesses hear the screams well enough to differentiate between a male and female scream?

To start his analysis Lin made an assumption that Reeva would have screamed at a sound level of 110 dBA. At How Loud Can a Woman Scream? we discuss in detail why we think this was an unrealistic assumption, chosen to support Oscar’s version and not to assist the court, as one would expect from an expert witness. Based on research a sound level of 120 dBA would have been a much more realistic and honest value. However, we will show that even with an assumption of 110 dBA the Reeva’s screams would still have been both audible and intelligible to the Stipps to the extent that they would have been able to tell the difference between a male and female scream.

The defence expert assumed that the closed bathroom window would have reduced the sound level of the scream by 25 dBA at a distance of 1 metre away from the window. He also assumed that a scream in the bathroom would be attenuated by about 9 dBA through the open bathroom window.

  • Sound Level in bathroom = 110 dBA (120 dBA)
  • Sound Level at 1 meter outside bathroom window = 85 dBA (95 dBA)

Using an acoustical formula one can calculate by how much the sound level would dissipate over a given distance. In his analysis Ivan Lin used a distance of 80 metres, while the actual distance is 72 metres. Another error in favour of his client. Over a distance of 80 m the SPL would decrease by about 38 dBA.

  • SPL on Stipp balconies = 47 dBA (58 dBA)

Whether these SPL’s would have been audible and intelligible depends on the level of ambient (background) noise at the time. The difference between the sound level of a noise (e.g. scream) and the ambient noise level is called the signal to noise ratio (SNR).

For sound to be intelligible we need an SNR of at least 6 dB. Intelligibility then increases as the sound become more audible. Ideally one need a SNR of 10-15 dB for good intelligibility.

Therefore another critical assumption that requires careful consideration is the level of ambient noise. The question is what would the ambient noise level have been in the Stipp bedroom at 3 am in the morning, in a sparsely developed residential estate – far removed from major sources of ambient noise such as busy highways or commercial and industrial zones

The defence expert assumed a range of 20 dBA to 45 dBA (apparently based on his own personal experience). This range is so wide that it is pretty much useless. The upper limit of 45 dBA is unrealistically high. Please read our research into Ambient Noise as to why we think an ambient noise level of 30–35 dBA would have been a far more realistic and honest assumption.

Why didn’t the defence rather measure the ambient noise level in the estate itself at 3 am in the morning? They didn’t because the results would have been detrimental to their case.

Based on a conservative ambient noise level of 35 dBA the SNR to someone on the balconies would have been about 12 dB (23 dB).

Larger than 6 dB makes it audible, and between 10 and 15 dB makes it very intelligible.


  • Screams from the toilet through a closed window would have been both audible and intelligible to Dr and Mrs Stipp where they stood on their balconies, irrespective of whether Reeva screamed at 110 dBA or 120 dBA.
  • Similarly, screams from the bathroom through an open window would also have been audible and intelligible to Dr and Mrs Stipp where they stood on their balconies.
  • The level of intelligibility would have been high enough for the Stipps to also discern the emotion in the screams – irrespective of whether Oscar or Reeva screamed, and irrespective of whether the screams were at 110 dBA or 120 dBA
  • The defence wasn’t honest when they argued – “when someone is in that toilet it is a closed confined space with a closed window and a closed door you would not hear a woman screaming and in any event not so distinct that you will make out emotion … if she was inside the toilet.”

Read more in our book Oscar vs. The Truth.

The Book : Oscar vs The Truth

By Thomas Mollett and Calvin Mollett

Buy now for only ZAR 125 (~USD 7.5, ~GBP 6.50) – PDF format- at

What really happened on that Valentine’s evening of 13 February 2013 when Reeva Steenkamp was shot and killed in the toilet of Oscar Pistorius’ house? Did Oscar know that Reeva was behind the toilet door? Or did Oscar truly believe that an intruder was hiding behind that door?

In this book, brothers Thomas and Calvin Mollett set out to find the answers by taking a painstaking look at the crime scene and evidence with eagle eyes.

• Was Oscar on his stumps when he broke open the toilet door?

• What do the clothes Reeva was wearing when the paramedics arrived tell us about the crime?

• Which of the witnesses were in the best position to hear screams from Oscar’s house?

• What caused the wounds on Reeva’s back?

• Did the prosecution present all the evidence?

• What does the cricket bat tell us?

• Was Reeva alive when she was carried downstairs?

These are only some of the questions addressed in this full-colour book of 80 000 words and over 500 high-quality images – a book that informs as much as it exposes.

Oscar vs the Truth is now available at