Acoustic Forensics: Investigating a murder with acoustic modelling

Ten years on from a fatal shooting, how can acoustic modelling help a team of forensic architects to answer key questions in the ongoing investigation of a high-profile murder?

Background
On 6th April 2006, 21-year-old Halit Yozgat was fatally shot at his family’s internet café in Kassel, Germany. His death was the ninth in a series of ten killings across Germany, targeting mainly migrant communities by the National Socialist Underground (NSU) – a Neo-Nazi group known to the German Intelligence Service between 2000 and 2007.

What was of special interest, in this case, was that a Domestic Intelligence Agent, Andreas Temme, was present in the café at the time of the shooting. Temme initially failed to disclose this to the police but then, after his online activity confirmed that he was in the vicinity at the time of the murder, he claimed to neither hear, smell or see anything of the shooting.

In the ten years since the shooting, it was further unearthed that there were huge gaps in the police investigation. Commissioned by the People’s Tribunal and working with the families of the victims, independent research agency Forensic Architecture, based at London’s Goldsmiths University, was appointed to help investigate the cold case and it’s at this point they approached Anderson Acoustics seeking our help.

Drawing from leaked photos and documents from the scene, Forensic Architecture commissioned a full-scale replica model of the 77m2 café to be built in Berlin’s House of World Cultures. The internal finish of the reconstructed café replicated the same internal finish so that the model would perform in the same way as the original crime scene. Full tests were carried out from pooling witness logs across desktop and mobile devices, as well as call records and testimonies. This formed a detailed timeline of activity in the café and highlighted the small window of time in which the murder could have taken place – firmly placing Temme in the building.

In addition to further testing and modelling for smell and sight, we investigated whether Temme could have failed to hear the shot as he claimed.

Methodology
Forensic Architecture contracted weapons experts Armament Research Services (ARES) to record the sound of the gun and ammunition used in the murder. They also recorded the sound of the weapon when threaded with both a dry and wet sound suppressor (silencer) to stimulate the suppressor used in the crime. None of the shots were suppressed to below 130 dBA.

In the reconstructed café, we placed a high-decibel loudspeaker at the position of the shooting to see how the sound propagated throughout the building. The internal finishes highlighted the vast use of highly reflective surfaces through the café, such as brick structures and glazing.

Using CATT Acoustic modelling software, the results from the physical reconstruction were used to calibrate a model re-enacting the murder. The image below shows the sound radiated from the gunshot, the time taken to reach Temme and the sound pressure level at his position.

Results
Our reports confirmed that the sound level at Temme’s ear position was 94-99dB Lmax, similar to the sound of a motorcycle driving past twenty-five metres away from you. Therefore, clearly audible in Temme’s position.

Our findings, along with those from experts in smell and crime scene investigation, concluded that Temme would have been aware of the incident taking place, therefore putting into question his testimony at the time and reopening the case in the search for the truth.

Forensic Architecture’s investigation was presented at the Hesson Parliamentary inquiry on 25th August 2017 highlighting that Temme must have perceived the crime.

The investigation continues.

Ongoing developments
To read further updates and see photos from the Yozgat investigation, visit the Forensic Architecture website here.

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