Digital data is far easier to manipulate than analogue data, a legal evidence expert testified at Judge Nkola Motata’s drunken-driving trial in the Johannesburg Magistrate’s Court on Wednesday.
”Digital data can often be seamlessly changed without any losses being apparent,” said University of South Africa criminal law Professor Daniel Petrus van der Merwe.
”It doesn’t require special training,” he said.
A trial within a trial was under way to determine the admissibility of five cellphone recordings taken on the night of January 6 2007. This was when Motata crashed his Jaguar into the wall of a Hurlingham property, allegedly while drunk.
Referring to digital data such as the cellphone recordings, Van der Merwe said digital guarantees of authenticity would be needed.
For example, he said there was software available that counted up every bit and byte of a piece of data and stored this information.
”If any subsequent change is made to the subsequent document, even a space or full stop, it will detect that change and that the integrity of the original mechanism has been lost.”
This kind of security measure was not taken with the cellphone recordings.
Damage to the cellphone meant that the original recordings on its random access memory (RAM) were lost. A secure digital (SD) card on to which the recordings were saved from the phone was apparently subsequently stolen.
The owner of the Hurlingham property, Richard Baird, who took the recordings, previously testified in court that the best evidence to use would be ”encrypted” copies of the cellphone recordings on his laptop.
However, the court was working with a different copy of the recordings. It had been listening to MP3 copies — a different format from the MP4 format they were originally captured in by the cellphone.
Van der Merwe said an ”encrypted” version meant it was data that ”has been stored by a specific device which means other devices might not be able to open it”.
He said in the absence of the original, or data that had electronic security measures sealing its authenticity, legally ”the value of such evidence will stand or fall by the witness giving such evidence”.
The integrity of the person’s interest in the data would become a factor. ”The digital data will not stand independent from that evidence.”
Van Der Merwe said there were particular difficulties in determining the admissibility of the data in this case.
”One of the biggest problems with digital data is that one is very reliant on the machine or the human with the machine.
”I think this is an especially problematic case because there are a multiplicity of machines and a multiplicity of files and the human selection of recording.”
He said the best data to use in the case would have been the recordings taken from the RAM on the cellphone.
”We are working now with second-generation evidence. It might even be third generation.”
The computer used to make the recordings the court was using was a new additional machine brought into the data-recording process after the cellphone and SD card, he said.
Earlier, mobile software developer Willem Frederick Jacobus de Jongh said it was possible to change the content of digital data without changing the time or date of creation of it.
It was also possible to change the time and date of creation without changing the content of the data. He said only forensic auditors might possibly be able to pick up any changes made.
On Wednesday morning the state closed its case in the trial within a trial after one of the witnesses it sought to call — a metro police officer — was booked off work indefinitely due to illness.
Motata is facing charges of drunken driving and defeating the ends of justice for allegedly resisting arrest. — Sapa