Oscar Pistorius – is THIS why he really is not guilty of murder?

When the trial of Olympic and Paralympic sprinter Oscar Pistorius resumes in the Pretoria High Court on Monday, both sides will be back trying to prove a 'whydunnit'. This trial has never been a 'whodunnit' – though it has been the most riveting example of 'carcrash' TV I've seen since the OJ Simpson spectacle.

Pistorius has always admitted firing four shots that ended girlfriend Reeva Steenkamp's life in horrific fashion behind a locked toilet door in his luxury Pretoria East home on Valentine's Day 2013. He has always denied premeditated murder after a heated argument, as the state contends. He says he mistook Reeva for an intruder and fired 'without thinking' because he was overcome with fear. 

In this blog, I reveal a 'whydunnit'  that could  better explain Pistorius's behaviour around guns, and  prove him right to claim he's not guilty of Reeva's murder

By Csho Chilala

The legal  team trying to save Oscar Pistorius from jail may have missed a brilliant trick:  the weapons effect. The trigger pulled his finger.

The weapons effect is a psychological term for the mesmerising effect the mere presence of a gun can have on minds and digits. It is based on research showing that guns "don't just permit violence, they stimulate it as well".

It could mean Pistorius was right all along  to say he isn't to blame for pumping four bullets into a locked toilet door, killing girlfriend Reeva Steenkamp in the most gruesome fashion on Valentine's Day 2013.

His gun is to blame. It is the "smoking gun".

American Dr Leonard Berkowitz, University of Wisconsin emeritus psychology professor,  first used the term weapons effect in a 1967 study in the Journal of Personality and Social Psychology, showing the effects of guns on body and mind. He has spent the intervening years contributing to a body of research into the weapons effect.

Among his findings:  "The finger pulls the trigger, but the trigger also pulls the finger".

Defence advocate Barry Roux claims Pistorius acted in "putative self defence" – he fired genuinely, but wrongly as it turned out,  thinking Reeva was an intruder lurking behind the toilet door.  One legal difficulty:  putative self defence weakens with the number of shots exceeding one.

Pistorius says he isn't to blame for four shots. His 9mm pistol is, because it's a semi-automatic. It fired in one burst, not "two double taps" – two shots, brief pause, two more – as Roux initially claimed, and witnesses testified they heard.

Pistorius also claims he fired "unconsciously"; at no stage did he "think about firing". Only problem is he also testified he did "think about not firing" a warning shot into the shower beside the toilet, in case a "ricochet" hit him. But no matter.

Pistorius could claim the weapons effect made him a latter-day "Manchurian Candidate", the unwitting lead in a "snuff" movie;  the gun that was his constant companion, even in bed, overcame all rationality, perspective and extensive firearm training.

That would account for the "eerie autonomy" guns seem to have in Pistorius's hands, writes New Yorker executive editor Amy Davidson; and for the "miracle of immaculate explosion" as state prosecutor Gerrie Nel sarcastically described an incident in which a Glock pistol fired in Pistorius's hand, while dining with friends in a Johannesburg restaurant.

Pistorius says his finger "wasn't on the trigger"; the Glock fired, despite a safety feature that "keeps it from discharging unless the person holding it has his finger fully on a sort of trigger-within-the-trigger and pulls", says Davidson.

The weapons effect might well explain the many examples the court heard of Pistorius's odd behaviour around guns; why on hearing a noise on an earlier occasion, and fearing  an intruder, he instantly dropped to the floor adopting "code red" or "combat mode", only to realise it was the washing machine.

Unlike Reeva, the washing machine emerged unscathed from that encounter.

Pistorius could claim the weapons effect was more devastating because his pistol fired four "Black Talon" bullets into Reeva. Also called "dum-dum" or "expanding" bullets, these come nattily dressed in "black metal jackets". They are about as ugly as ammunition gets.

In evidence for the prosecution, forensic pathologist Dr Gert Saayman described the dum-dum's violent effects, evoking imagery that verged on poetic in juxtaposed detail: It "folds out like petals of a flower", Saayman said, petals that are "furthermore designed to have very sharp jagged edges". It is deliberately designed to cause "maximum damage" when aimed at a target of human tissue.

One bullet made Reeva's head "explode like a watermelon", Nel said, referring to the "Zombie stopper" video of Pistorius blasting the fruit to smithereens at a shooting range, allegedly with the same pistol that killed Reeva a few weeks later. The athlete is heard to say, after poking the watermelon's mangled flesh: "It's a lot softer than brain, but ****  it's like a zombie stopper".

Another bullet carved Reeva's arm "like an instant amputation", forensic geologist Roger Dixon testified for the state – in a rare comment in evidence that made any sense at all.

One might idly wonder what Pistorius was doing with bullets South African soldiers and police aren't allowed. His gun "required" them, he said – an involuntary anthropomorphic allusion signalling weapons effect, if ever I heard one.

Psychologists might say the effect grows stronger with attachment. Witnesses, including Johannesburg firearm trainer Sean Rens, have testified to Pistorius's "great love", and "enthusiasm" for guns, and an arsenal on order: three shotguns, two revolvers, a semi-automatic assault rifle, another self-loading rifle and nearly 600 ammunition rounds.

Psychologists debate whether the weapons effect is real. Some research discounts it. Other research replicates it: A 1990 review in the Journal of Personality and Social Psychology of 56 studies, confirmed that the mere sight of weapons can "increase aggression in both angry and non-angry people". In Accident Analysis and Prevention in 2006, Harvard scientists show that drivers with guns in cars are more likely to drive aggressively.

Experts say the symbolism and impact of guns vary, depending on "a given individual's consciousness". For some, they are a source of safety and security, fulfilling one of the most basic human needs in psychologist Abraham Maslow's hierarchy. For others, guns sublimate sexual needs.

The sexual symbolism of guns is subject to interpretation, especially in Freudian terms, yet practically every weaponry class, from bullet to bomb, has been associated with phallic symbolism. Last year, in a interview in Foreign Affairs, retired US Army general Stanley McChrystal said of his role in directing weapons use in Iraq: "It is sexy, it is satisfying, it is manly."

A gun can have "dark presence", writes New Yorker journalist Alec Wilkinson, and be about "possession of a tool that makes a person feel powerful nearly to the point of exaltation". He's not saying everyone with an "inordinate" passion for guns is unstable, just that a gun can be "the most powerful device there is to accessorise the ego".

Reeva's death demonstrates the fatal consequences.