National Post

August 3, 2007

Identical and deadly
Joseph Brean, National Post

The evil twin is a staple of both high-brow mythology and low-brow schlock.

From Romulus, the feral demi-god child who murdered his twin brother Remus to take control of ancient Rome, through to the nasty sister on I Dream of Jeannie, evil twins have been driving fictional plot lines for as long as writers have been looking for a plot twist to capture the public imagination.

That imagination was kicked into high gear this week in Surrey, B.C., when police announced they had arrested Jason Robert Weismiller, 27, on suspicion of second-degree murder in the stabbing death two weeks ago of his identical twin brother, Darryl James Weismiller.

"Have we got the right guy? Are we sure that it was Jason? I don't know. I'll have to call you back," said RCMP Corporal Dale Carr, before confirming that the brothers can be distinguished by identifying marks on their bodies. He said police are satisfied there are no other suspects.

The question of twins doing harm to each other is as perplexing for psychologists as it is for police, especially in the case of genetically identical "monozygotic" twins, because it flies in the face of everything that is known about their emotional tendencies toward each other.

But when it happens, twin-on-twin violence provides valuable clues to human nature. Even as the exception to the rule, it helps scientists to tease out the competing and complementary influences of nature and nurture, just as scriptwriters have done in the more memorable episodes of Knight Rider, Star Trek or South Park.

"There's no such thing as twin aggression. I don't know what that means," said Nancy Segal, director of the Twin Studies Center at California State University, Fullerton, who called the case "an aberration in terms of what we know about how twins react towards one another."

She said studies show the twin relationship is more intimate than that between non-twin siblings, and that identical twins are closer than fraternal (non-identical) twins. That bond even seems to transcend generations, as identicals appear to be closer than fraternals to their nieces and nephews.

"Twins will tell you it's just the closest relationship they have," she said. "Twins do have their rivalries. You find the competition between twins is of the order of one twin does something, the other one figures they can do it too... But this kind of thing [murder], it seems to me, would only happen if there were some predisposition towards aggressive behaviour, irrespective of twinship. I mean, what causes a criminal anyways?"

There is little in what is publicly known about the Weismiller brothers that hints at violence, other than unconfirmed reports of an argument at the time of the killing. Both were unemployed, and both have been arrested in the past over such petty crimes as theft. Neither is known to be a serious criminal.

The Vancouver Sun reported that Jason has two sons, ages two and eight, and that Darryl did not usually stay at the home where the killing occurred, which is owned by their father. Their mother is estranged from the family, police say.

And of course it remains uncertain what role, if any, twinship played in the circumstances of Darryl Weismiller's death. At the very least, though, the stabbing marked the end of a relationship that, according to the statistics, should have been intimate and loving, if not occasionally fraught with rivalry.

Tony Vernon, a University of Western Ontario psychology professor who heads up a survey on twins, said in an e-mail that identical twins "typically do have a very special relationship with one another quite unlike that enjoyed by any others - even husbands and wives - and their relationship can manifest itself in a wide variety of forms ranging from extreme closeness to extreme competitiveness."

Murder, however, is rare.

In Canada, roughly 37% of solved homicides are committed by a family member, but only 2% by a sibling, known as a fratricide. In a survey of Quebec coroners' files from 1991 to 2000, for example, Dominique Bourget and Pierre Gagn found 10 fratricides, with mostly male victims and offenders. The only twin fratricide, by a female, was notably the only one in which the offender had depression.

In the United States, the most prominent example is of Jeff and Greg Henry. In Georgia in 1991, when both were 35, Jeff killed Greg, his smarter and more dominant twin brother, with a shotgun blast to the chest.

"He was my life," Jeff would later tell John Glatt, a true crime writer. "He was me. The only reason we fought was that I wasn't him. He would get angry at my weaknesses. He wanted me to be more like him."

Another was the 1996 trial in California of Jeen Han, then 22, who had recruited two teenage boys in a failed plot to kill her identical twin sister, Sunny.

The case attracted huge attention from the post-OJ media, which was rewarded when Jeen sold her story mid-trial to the tabloid TV show Hard Copy. Sunny would later attempt suicide with pills after her first day of testimony and be unable to continue. Jeen was convicted nonetheless.

"I was just curious, so I went on a database to see homicide, twins.' There's nothing," said Neil Boyd, a criminologist at Simon Fraser University.

"There's a lot of literature out there that deals with identical twins and crime, but it all looks at the nature-nurture split, and basically what that research tends to tell us is that identical twins raised apart are more likely to have similar criminal profiles than even fraternal twins raised together or brothers and sisters raised together. In other words, our assumption that environment drives criminal behaviour has been tested, in fact has been seen as quite problematic, given the results of the twin studies," he said.