Both Gert Saayman and Johan Vermeulen are applied scientists. Both hold a number of formal qualifications that saw them trained in forensic investigations. Both have plied their respective trades for decades. Both have much experience in acting as expert witnesses in criminal trials, and explaining their sometimes complex findings to courts.

But in the second week of the trial of Oscar Pistorius for the killing of Reeva Steenkamp, forensic pathologist Saayman and ­materials analyst Vermeulen had very ­different experiences in the witness box, vividly illustrating both the advantages and the pitfalls of matching the scientific method to a system of adversarial justice.

All indications are that judgment in the Pistorius murder trial – a case that prosecutor Gerrie Nel himself described as circumstantial – will hinge on various branches of forensic science, from ballistics to pathology.

There is every reason to believe the findings drawn from the science will be highly contested; Pistorius’s defence team has lined up experts to counter witnesses called by the state.

Defence lead advocate Barry Roux SC did not wait to call his own witnesses to begin the legal assault on the state’s version of events on the night Steenkamp died.

Unusual strategy
Continuing an unusual strategy implemented during bail proceedings a year ago, when Pistorius submitted a highly detailed account of the night, the defence team made no secret of the sequence of events it will present to the court – a sequence it will argue shows Pistorius did not commit murder.

It was an approach that saw Vermeulen mauled by Roux during cross-examination, pushed to participate in sometimes bizarre ­physical demonstrations of the cricket bat and door he had been tasked with examining, and forced into joining ever more complicated speculation about plausible and implausible sequences of events.

Saayman, by contrast, had an easier time under cross-examination earlier in the week, with most of his findings and many of his conclusions from Steenkamp’s autopsy accepted as presented.

The difference seemed rooted in a difference of approach.

The meticulous Saayman described a process that differentiated between observation and interpretation, providing a few hypotheses gingerly, with many caveats. He presented work almost entirely free of assumptions – but also of hard, testable findings.

Two approaches
Whereas Saayman laid out measurements and then spoke in terms of probabilities, Vermeulen provided what he considered likely scenarios, then explained why he had reached the conclusions he had. Saayman’s language was peppered with precise medical terms impenetrable to the lay person and requiring less precise explanation; Vermeulen used vaguely defined words and phrases imprecise enough to make an academic cringe.

Yet the decidedly more blue-collar approach to finding the truth taken by police employee Vermeulen may be preferable to Saayman’s more scientifically pure approach in a court.

“You want information put to you, but you also want to have a version that silks [senior advocates] can bash around [to] see if it stands up,” explained a court officer not involved in the matter. “If a guy is saying, ‘this is what I think happened’, that is a witness we can evaluate. If a guy says, ‘here is what I measured’, it can lack meaning.”

State witness and materials analyst Johannes Vermeulen. (AFP)

But had each been defending a thesis outside a court, or been subjected to peer review of a paper, Saayman would have succeeded where Vermeulen would fail.

Both men presented evidence not in keeping with the version of events Pistorius described on the night of Valentine’s Day 2013, before and after he shot Steenkamp. Pistorius said the couple had turned in for the night hours before midnight; Saayman said Steenkamp might have eaten something several hours later. Pistorius said he was wearing his prosthetic legs when he broke down a door to reach Steenkamp; Vermeulen said it appeared that Pistorius was so low to the ground at the time that he must have been standing on his stumps.

Worlds apart
The manner in which they presented their findings was worlds apart. Saayman delivered what was, in effect, a mini-lecture to explain the caveats that went with his finding of when Steenkamp had had her last meal.

He noted that this problem had been closely studied because it is both important in investigating murders particularly fraught with difficulty.

He described the imprecision of the science involved. He cited the possibility of very large meals, or very small meals, affecting the time taken to digest food.

He cautioned that different types of food are digested at different speeds, that different people digest food at different speeds, and that the same person could digest food at different rates from one day to the next.

He explained that food continued to be digested after death. Only then would he allow that the probable time between meal and death was, probably, approximately, two hours.

No prosthetics
Vermeulen, on the other hand, presented his theory that Pistorius was not wearing prosthetics when he broke down the toilet door in what Roux would later refer to as an “ambush” (the finding was not contained in the written report Vermeulen had compiled).

Vermeulen then found himself defending that theory from a furious attack by the defence counsel, at one point being made to balance on his knees but with his feet in the air – trying to swing a cricket bat. Roux pushed hard: What constitutes an “unnatural” position in which to swing a cricket bat? How many ­positions were actually tested?

If the police stood in service of the accused as much as the prosecution, as Vermeulen said, why was a version of events presented by Pistorius not tested under laboratory conditions?

Vermeulen, at times with a bemused expression, found his hypothesis gradually eroded through small concessions and new caveats.

To lay watchers, it appeared that Vermeulen was demolished by the defence, while Saayman held his ground.

Basic principles
To scientists working in the rarefied air of academia, it appeared that Vermeulen had ignored basic principles; Saayman stuck to them.

To police with a job to do, one officer commented, it seemed that Saayman lacked the guts to point the finger of accusation, whereas Vermeulen did his job.

To some judicial officers, it seemed Vermeulen provided a testable version of events, even if it were found wanting, but Saayman’s approach left the court to interpret his data with too little guidance.

All of which is, of course, irrelevant, and how Judge Thokozile Masipa interpreted the evidence of each expert will only be clear when she provides a summary of evidence before delivering the verdict.

If theory holds and the history of complex cases is any guide, the court will not see any individual witness or single piece of evidence as either bolstering or undermining Pistorius’s version of events, nor will it point to a smoking gun proving whether or not a murder was committed.

Instead, it will consider all the information before it: as pieces of a puzzle to be weighed and tested against one another – measured for import and plausibility, and carefully fitted into the whole.

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Two more weeks for trial

Counsel for the state and defence in the murder trial of Oscar Pistorius on Thursday said they had agreed to continue his trial for an additional two weeks before planning further dates.

The new dates had not been ratified by the court at the time of publication, but that was considered a formality.

The case was due to be heard between March 3 and March 20, but halfway through that period it was evident that far more time would be required – with prosecutors still painstakingly building a case and state witnesses subjected to lengthy cross-examination.

The trial is now expected to continue without interruption until April 4, with an assessment to be done towards the middle of April on how much further court time will be required and to agree on dates. – Phillip de Wet