CLIFF FALL IN SYDNEY

By Rod Cross, Physics Department, Sydney University. April 2009

In November 2008, Gordon Wood was found guilty of throwing his girlfriend, Caroline Byrne, off a cliff at The Gap in Watson’s Bay. Some of the forensic evidence presented at his trial can be found in the Journal of Forensic Sciences (2006) article and some additional information is provided here. Physics Today included an article on this case and other forensic physics cases in the March 2009 issue.

Less than 10% of the information I presented to the police was presented at the trial, presumably because of the technical nature of much of that evidence and because of the limited time available for the trial. The defence were given access not only to all of that information but also to handwritten notes, 278 email messages to and from the police and to all video film of experiments undertaken over the five year period from 2003 to 2008. It is not certain whether they understood it, judging from the following exchange at the trial:

TERACCINI: 5.8 metres is just that, isn’t it Professor? If the rate is 5.8 metres, that’s what it is, isn’t it?

A: No.

Q: No?

A: No. Yes, no.

Q: You agree, don’t you?

A: No. I don’t agree with what you are saying.

Q: If you have a person running 5.8 metres.

A: Per second, you mean?

Q: Yes. That’s the rate they run, isn’t it?

A: No, that’s the speed at which they run.

Q: I’m sorry, speed they run, correct?

A: No, that’s the average speed over the whole 50 metres of their race.

Q: Yes. If we break it down, it’s 5.8 metres per second. Correct?

HIS HONOUR: I don’t understand the question. Can you break down an average speed?

Q: If you jumped in an elevated fashion, do you agree that you could rotate and land on your head?

HIS HONOUR: The answer is Yes, if you impart torque at the point of departure and No if you don’t.

TERACCINI: Thank you, your Honour. Is there no way of knowing whether you will rotate or you won’t when you jump off with the elevated broad jump?

TEDESCHI: I object. I don’t understand the question.

TERACCINI: Do you agree that there’s no way of knowing whether you would rotate or not?

TEDESCHI: I object to the question. It’s a meaningless question.

HIS HONOUR: It’s a meaningless question. Move on, Mr Terracini.

Q:  Does it make any difference to how long it takes to fall if a person is flailing arms, flapping legs, things of that kind?

A: No.

Q: What about the angle or the part of the body that first comes into contact with the hard object at the bottom?

A: What about it?

Q: Do you hold yourself out to be an expert in gait analysis?

A: I have written one paper on that subject, so that makes me an expert on that particular part of the subject.

Q: And what particular part of gait analysis have you published?

A: The paper of mine that you previously quoted on walking, running and jumping on a force plate.

Q: And the force plate is used for what purpose?

A: The measurement of the force on the ground.

Q: Does it have anything to do with falling? It doesn’t, does it?

A: No. There is no force on the ground when you are falling through the air.

And so on. At the committal hearing, Terracini made the comment that human motion cannot be studied using physics since the human body is much too complicated. As an example, he said

“Not everybody can hit a golf ball like a champion. It’s self-evident. It’s got nothing to do with physics. Nothing. It’s got to do with your ability.”

In fact, the swing of a golf club can be accurately modelled as a double pendulum. If the laws of physics had nothing to do with swinging a golf club, then golfers could presumably hit a golf ball just as far with a 20 gram club as with a 400 gram club. In fact, they wouldn’t have to hit the ball at all. They could simply use will power or spiritual guidance.

My conclusion from all of this is not that barristers should learn elementary physics but that the jury system is fundamentally flawed when it comes to the examination of expert evidence. The evidence should be carefully examined in the first instance by other experts, not by barristers, not by the police and not judged by a lay jury.