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Wednesday / February 21.
HomemistoryAccidental Detectives

Accidental Detectives

A pair of bloodied glasses at a crime scene… the victim of a freak road accident wearing blue-tinted sunglasses at night… a multiple homicide and spectacles with an unusual script. Sounds like the basis of a plot for CSI: Crime Scene Investigation, but the world of ocular forensics is far more like solving a difficult cryptic crossword.

The police announcements are routine enough. Anyone with information on the wanted criminal is asked to contact Crime Stoppers… the wanted person has been using that alias, was last seen in this area, can be identified by that tattoo; this birthmark… or this spectacle script.

When the Victorian Police Fugitive Task Force recently hit yet another dead-end in their search for cold-blooded killer Graham Gene Potter, they turned to optometrists, releasing his last known glasses prescription.

Potter, once a trusted lieutenant to powerful mafia identities, vanished about five years ago while facing serious criminal charges. There have been no confirmed sightings of Potter since 2010, when he bought glasses. (His script then: R -1.75 -0.75 x5, L -1.75 -0.50 x174. His pupillary distance was 64. His previous frames were Eschenbach model 820519 size 54 – 18 colour 30.)

When the Victorian Police Fugitive Task Force recently hit yet another dead-end in their search for cold-blooded killer Graham Gene Potter, they turned to optometrists

Most often, appeals such as these don’t produce results, but for Emeritus

Professor Graham Strong and Professor Gordon Sanderson, chance requests for assistance by police on opposite sidesof the globe, in Canada and in New Zealand respectively, have led them both to a lifelong passion for – and accidental careers in – the highly specialised field of ocular forensics.

Both men confirm the reality that forensic science is less CSI – with its high-tech gadgets that quickly solve heinous crimes in a neat forensic package – and more like trying to solve a complex puzzle… sometimes with half the pieces missing.


Professor Strong, Emeritus Professor in Optometry and Vision Science at the University of Waterloo in Ontario, Canada (now retired) said he fell into forensic optometry by “happenstance”

in 1989, when a police officer phoned his clinic, asking for assistance. “Police divers had recovered a pair of eyeglasses in a swamp near where the body of a dead young woman was found. They had a person of interest who was a habitual spectacle wearer. The suspect had recently purchased new glasses because his old pair had been lost.

“The eyeglasses recovered from the scene were very similar to those that had been dispensed to the (suspect), and were now missing,” he said.

Canadian police had the man’s optometric records and wanted to know whether it was possible to determine whether or not the eyeglasses in evidence were the same eyeglasses that had been dispensed to the accused.

“I had no idea how to approach this challenge, but I was sure that I could figure it out – which I did – and a forensic optometrist was born!”

In much the same manner, in Dunedin, New Zealand, Gordon Sanderson, was also unwittingly drawn into a secondary career as an expert in ocular forensics after being called on to assist in an extremely high-profile multiple homicide.

David Cullen Bain was convicted in May 1995 of the murder of his parents and three siblings in Dunedin in 1994. He served more than 13 years of a life sentence before an appeal lead to his conviction being quashed. A retrial ended with his acquittal on all charges in 2009.

Now Associate Professor at the Dunedin School of Medicine where he teaches undergraduate and postgraduate ophthalmology, Prof. Sanderson was asked to help police establish ownership of a particular pair of glasses in evidence. Although he’s never sought work as a court expert, Prof. Sanderson is now on his 28th case. “I’ve never advertised… there seems to be a network among lawyers”. His name is obviously top of the list when it becomes apparent there is a vision element to the case.

A Labour of Love

While the two men have been in fairly constant demand as expert witnesses in their respective judicial systems, they’re quick to point out that a high profile is no guarantee of financial reward.

“I don’t think I ever even recovered my out of pocket expenses, but I sure loved the work,” said Prof. Strong. His Kiwi counterpart agrees: “You charge by the hour… but you wouldn’t make a living out of it”.

Countless hours can be spent investigating or consulting on a case, which may – or may not – wind up providing useful evidence. The case may – or may not – go to trial. If a matter does go to trial, an expert witness is directed to appear at the convenience of the court, submitting to examination and cross-examination by both the prosecution and defence. They’re expected to provide impartial, scientifically rigorous evidence that can be understood by those with no background knowledge of optometry or ophthalmology – the judge and/or jury.

Needless to say, it can be a nerve-wracking ordeal that in some cases may have to be repeated more than once, as a case progresses through the judicial system, particularly if appeals are involved.

And while courts expect expert witnesses to appear on time and when required, the convenience of the expert witness is not a consideration.

“Funny story: I actually missed my honeymoon trip to Australia in 1990 because I was subpoenaed for a court appearance in a murder trial in … Ontario,” Professor Strong recounted.

“My wife travelled to Australia without me because we were scheduled to give several papers at the International Low Vision conference that year. It was to be a clever and opportunistic blending of business with pleasure.

“I cancelled my trip in order to appear at the trial. However, when I arrived at the court on the scheduled trial date… the hearing had been postponed at the last minute and was being rescheduled… My wife and our colleagues had a great trip to Australia, and we celebrated our honeymoon at home when my wife returned,” he mused.

Commitment to Truth

Prof. Sanderson said utmost in mind, when consulted on ocular forensics, is an obligation to the truth.

“Either working for the defence or the prosecution, you can’t be biased. There are laws about being an expert witness, and you have got to be objective… you must never twist your advice or evidence. As a result, they (lawyers in a particular case) may choose not to use you.

“You have to give an opinion, and then must be able to defend it.”

Prof. Strong said his personal commitment was always to investigate and present evidence “fully, objectively and truthfully so that the rights of the accused and of the victim(s) are held in high and equal regard”.

“Anyone who has read John Grisham’s non-fiction book The Innocent Man: Murder and Injustice in a Small Town is aware how justice can be derailed by flimsy or flawed science with disastrous consequences.

The Innocence Project1 provides a shameful array of similar cases.”

Prof. Strong said he always began his analysis with a presumption of innocence.

“In other words, my hypothesis is that the glasses from a crime scene do not belong to the accused. This is what I set out to prove. If this assumption leads to an obvious contradiction, impossibility, or falsehood, the initial assumption is disproven (reductio ad absurdum – proof by contradiction).

Ergo ipso facto, my hypothesis must be rejected, and I must conclude that they are the same glasses.”

Prof. Sanderson said his exposure to the legal system had made him realise there was “a lot of mythology about eyes… people have misapprehensions about vision and it is often hard to shake their views”. He cites, as an example, a belief that photographs can be manipulated to faithfully reproduce what can be seen by particular people in particular conditions.

Types of Cases

While both men have been involved as expert witnesses in high profile murder cases, Prof. Sanderson said many of the cases he consults on involved traffic accidents where he was called on to determine what people could see in particular instances.

These cases, he said, were particularly tragic, with the accused often as distraught as the families of the victims.

For example, there was the man who was driving into the sun, turned a corner and hit a pedestrian, who was not in a pedestrian area, and was perfectly camouflaged – her clothes matching her surroundings. There was the driver who killed a motorbike rider. The bike rider had been wearing dark clothes and was against the background of a high hedge. It was early morning, and the bike’s reflectors were covered in mud. Again, a series of events that culminated in senseless tragedy.

While Prof. Sanderson seems to have specialised in vision, in Canada, Prof. Strong has made his reputation with spectacle comparison.

He said when organising spectacle comparison evidence, the four essential considerations were: frame (size, colour and style); prescription (right eye Rx combined with left eye Rx); fabrication features (lens material, edging, tint, lens type etc.); and adjustment and fitting (individualised adjustments to suit the wearer).

“These are the specifications/features that are measured/observed and recorded to describe the eyeglasses in evidence. This is carried out by someone who is ‘blind’ to the information contained in the file describing the dispensing origin of the glasses worn by the accused… allowable manufacturing tolerances are used to describe acceptable variations when comparing these data. Additional allowances are noted based on any verifiable or known repair history for the accused’s eyeglasses,” Professor Strong said.

“If there is a complete match, this simply means that the eyeglasses from the crime scene are ‘the same as’ those dispensed to the accused. But, it does not necessarily mean that the eyeglasses from the crime scene are the ‘self-same’ glasses that were dispensed to the accused. Perhaps there are two or more people with exactly the same eyeglasses? The probability of there being multiple pairs of identical eyeglasses is directly proportional to their level of ordinariness…

“Using biometric and demographic data, it is possible to estimate the levels of uniqueness for each component within the four previously mentioned categories: frame, prescription, fabrication, and adjustment/fitting.”

The ‘Yahoo’ Moment

One of his most famous cases was profiled in the TruTV crime show, in an episode entitled Quite a Spectacle. Thirty-three-year-old Deborah Timlock was sexually assaulted and stabbed, in the Canadian town of Collingwood, Ontario, in 1989. The primary clues were a squashed tomato, complete with a shoe impression, and a pair of metal frame eyeglasses.

Police investigators had zeroed in on a former neighbour, Jim Brown, and while the shoe impression in the tomato proved a match, it wasn’t enough to convict.

Professor Strong was asked to determine whether the glasses left at the scene were the same as those worn by Brown in a grainy police mugshot on file.

A flash reflected in the man’s eyes in the mugshot enabled Professor Strong to calculate the PD and more than 20 other measurements, proving the glasses in the photo and those recovered from the crime scene were one and the same.

In the TruTV episode, Forensic Identification Officer Carmen McCann said he remembered hearing Professor Strong’s evidence for the first time, “like it was yesterday… this was months after the initial investigation. This was a piece of evidence that was individual and it truly was a ‘high-five, yahoo’ moment because now we were able to speak for Debbie Timlock”. Brown was convicted and sentenced to life imprisonment.

Spectacle identification also was a feature in the case against Canadian serial killer Allan Legere, who became known as

“The Monster of Miramichi”.

Legere had escaped from prison, where he was serving time for three murders. While on the run, he committed four further murders. After a possible Legere sighting and chase, a pair of eyeglasses were recovered.

The glasses were the same type, style and prescription as those worn by Legere, when he escaped from custody. While the prescription was very common, the frame was unusual. Professor Strong eventually identified a discontinued European frame.

“Only six such frames had been sold in Canada, all to prisoners in the penitentiary system. Five of these prisoners remained in custody, and still had their eyeglasses,” Professor Strong said.

From The Case Files

The following examples of forensic optometry have been provided from the case files of Professor Strong in Canada.

Investigators discovered a pair of binoculars that they believed was used to stalk a murder victim because the officer noticed they were in perfect focus to observe the victim’s windows. Turned out that the suspect had a significant refractive error that required him to make this focus adjustment to look at the bird feeder in his backyard.

A highly myopic suspect claimed he was unable to see the person he was stabbing because his glasses had been knocked off. Although he was ‘legally blind’ at distance, as claimed by his defence lawyer, his near vision was excellent.

A lens fragment was recovered in the immediate vicinity of a botched robbery, where the storeowner had been killed. The lens fragment was definitively linked to a broken pair of eyeglasses recovered from the home of one of the young suspects.

And from the case filesof Professor Sanderson, in New Zealand:

A man driving a 4WD towing an aluminium trailer containing a vintage car, hit and killed a woman in a car accident. The man claimed he was blinded by a flash of light. By working out the precise angles, Prof. Sanderson was able to deduce that the sun had hit the aluminum trailer, and flashed into the rear vision mirror, blinding the man at the precise moment when the woman pulled out, just as he had claimed.

A motorcyclist hit the back of a parked truck at night and was killed. The owner of the truck was prosecuted – even though he was inside his house at the time – because he had not left his parking lights on. Investigators found the motorcyclist’s crash helmet and blue-tinted sunglasses on the flatbed of the truck, which was also blue. The evidence was that the motorcyclist had lost his goggles, and instead wore his sunglasses to stop insects getting into his eyes, even though the glasses were not supposed to be worn at night. The blue-tint to the glasses at night made the blue truck almost invisible, and, therefore, the court found he had contributed to his own death.


1. The Innocence Project was founded in 1992 by Barry Scheck and Peter Neufeld. See www.innocenceproject.org.