Colonel JG Vermeulen demonstrates the effect of hitting a bathroom door with a cricket bat during the trial of Oscar Pistorius in the North Gauteng High Court in Pretoria. Photo: Alexander Joe

Pretoria - I’ve never been to Colonel Johannes Vermeulen’s laboratory, but I’d hazard a guess he isn’t assisted by a blonde in a lab coat. His machines probably don’t glow neon green and analyse data in a few seconds. The forensic science laboratory in Pretoria is not CSI. It’s not telly. There is no script, only messy crime scenes and the reality of being under-resourced and under-staffed.

This perception of ours, that because Vermeulen didn’t have all the answers he’s incompetent, is called the CSI effect.

This effect has been chronicled and researched in scientific journals such as Forensic Science International. As the public, we think forensics is hard, absolute truth and that all crimes everywhere can be answered precisely by it.

On Wednesday in court, Vermeulen hinted at some of the practical complications when he said that the investigation of the door should be seen “in the light of my doing a variety of investigations”.

But as defence advocate Barry Roux doled out questions to Vermeulen, it seemed he had done a fair bit wrong.

Where were the little splinters? What were those footprints on the door? Where was the door kept? Why hadn’t he asked? Some had joked Roux would accuse the door of lying, and by the end, they weren’t wrong.

“People have this perception that forensic evidence does not lie, but to a certain extent it’s tangible evidence that sometimes makes the full puzzle, sometimes 50 percent, sometimes 20 percent,” said Dr Jackie de Wet, forensic criminologist and forensic psychologist at the University of KwaZulu-Natal.

“It’s the defence’s job to cast doubt on the version that the State has put forward. To say ‘We found this, why didn’t you look at that?’ They have to ask the tough questions.”

The ball-crunching questions for the State will be: Why was evidence changed or lost? Why were procedures not followed?

Potentially they will argue that there is no such thing as a perfect, uncontaminated crime scene. “Crime scenes are hectic, they really are a mess,” said De Wet.

Investigators, forensics, photographers all scramble to get their piece of the pie.

Forensic scientist Dr David Klatzow said 90 percent of the scenes he had dealt with had been contaminated.

“If everybody had to work with a perfect scene, that would be lovely. But it’s very rarely the case,” said Klatzow.

“You have to dissect out from what’s left, what’s relevant and not what’s not relevant.”

He said mishaps, like the missing small pieces of the door, would weaken the State’s version but it would certainly not stop that story being told.

“The more precise you are, the less room there is for cross-examination,” said Klatzow. He said it would remain to be seen how much doubt Roux could sow in the mind of the court.

De Wet said it was unlikely, anyway, that something like a footprint on a door had genuinely destroyed any evidence. But such mistakes could add up and eventually impact on the validity and the relevance of the physical evidence collected.

“Evidence contestation can bring cases down,” said De Wet.

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The Star