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The Smiling Doctor and the Almost Perfect Murder


TRUE STORY: Two people were found dead in a locked car with the windows shut.

Medical reports confirmed carbon monoxide poisoning.

A family member later reported that both were unhappy, and one had expressed suicidal thoughts.

The conclusions were inescapable: if it wasn’t a terrible accident, it must have been suicide, or murder-suicide.

Whichever of those it was, it was a family tragedy, and there was nothing about the case that implied foul play.

Or was there?


The story began so innocently. A woman out jogging on a road in Hong Kong’s countryside noticed two people in a car which had pulled over at the side of the road into a bus layby.

They seemed to be sleeping. It was a damp day in the rainy season, and the car engine was on: she could see the windscreen wipers moving. There was nothing particularly suspicious about the scene. Perhaps the driver had stopped for a rest.

It was only later, when the jogger was returning from her run, that she began to be suspicious.

The car was still there. About 45 minutes had passed, but the two people had not moved.

But it was when she noticed the windscreen wipers that her worries intensified. They were still moving back and forth, back and forth, although the rain had stopped a long time ago. The rubber was scraping across the dry surface of the glass.

Why had neither of the women turned the wipers off?

Was something wrong here?

The jogger reached for her phone to call the police.


Officers arrived quickly and broke into the locked car, a Mini Cooper. Emergency medical staff took the women out of the vehicle and rushed them to the nearest hospital in an ambulance, lights spinning and siren blaring.

But the conclusion was all too obvious. Everyone at the scene could see that the women were dead. The two individuals, one of whom seemed to be a young relative of the other, appeared to have died of carbon monoxide poisoning in their car.

They were quickly checked by doctors at the Prince of Wales hospital in Shatin and declared dead.


Back at the scene on Sai Sha Road, near the town of Ma On Shan, officers noticed that there was no hose-pipe connecting the exhaust pipe to the main cabin through the car window.

But police knew that that was not really an issue. These days, catalytic converters remove 99 percent of the carbon monoxide from the exhaust, so that easy way of killing yourself – although common in TV shows and movies – is much harder to achieve in real life.

So how had the carbon monoxide got into the car’s main cabin? Some kind of mechanical defect must have caused the poisonous gas to seep into the car’s seating area. But how that happened was just a detail. The main story was that a family tragedy was unfolding in front of them. Somewhere in this city people’s lives would be changed by knowledge of this. The top priority job would be to trace the other members of the family.

Every adult in Hong Kong carries an identity card, so it was easy for police officers to move on that front. The older one was Wong Siew Fing, 47, originally from Malaysia. The younger one was her daughter Khaw Li Ling, called Lily, just 16.

Police set out to track down the woman’s husband Khaw Kim Sun, 53. In a painful coincidence, they discovered that he was a teaching doctor working at the hospital to which the women’s bodies had been taken.

They reached him late that afternoon as he completed a three-hour session with more than 250 third-year medical students.

Dr. Khaw was devastated by what he heard. He told police that he had four children aged between 12 and 20: three girls and one boy. He would have to break the horrible news to the remaining three children that they had lost their mother and sister.


A post-mortem examination quickly confirmed that the women had died from carbon monoxide inhalation. The report said both had 50 times the normal levels of the gas in their bloodstreams.

By the time the incident had entered into police records and details were being released to the press, the incident still appeared to be an unavoidable tragedy that had hit a high class family – and classy they were. Khaw Kim Sun was an anaesthesiologist and a university professor, with a comfortable home in the countryside.

He was not the introverted nerdy lecturer characteristic of Hong Kong universities, but a man with style and flair. He liked to wear old fashioned shoulder braces to hold up his trousers, and was considered handsome, the boyishness of his features contrasting with the grey streaks in his thick black hair.

Police quickly worked out the hour-by-hour story of what happened that day.

The six-person Khaw family lived in a nice home in Tai Tung Tsuen, Ma On Shan.

Both parents had been at home in the morning. The husband, an associate professor at Chinese University of Hong Kong, had left at about 1 pm to go and conduct a three-hour session with students.

The mother had stepped out of the house at about 2 pm with her daughter Lily. They climbed into the mother’s yellow Mini Cooper to go and pick up Lily’s siblings from school.

Using her phone, Lily had a brief conversation by text with a friend at about this time.

But Mrs Khaw and her daughter never reached the school.

They had travelled only a mile or so (1.6 km) along the main street towards town, on Sai Sha Road, when they stopped the car in a bus layby.

Apparently the gas leak must have made Mrs. Khaw woozy – and she had been alert enough to pull her vehicle off the road to prevent an accident.

Perhaps they were already too far gone to save themselves. They never managed to open the door and get out of the car, but quickly lost consciousness and would have been killed by the toxic gas minutes later.

The first witness who remembered seeing the little car was a bus driver who passed the spot about 25 minutes after they had stopped in the layby. Later still, the jogger had seen them twice, and called the police.

As the news broke, there was a huge outbreak of sympathy for the family. It was obvious that from that date, 22 May, 2015, their lives would never be the same.


Behind the scenes, police officers decided they should wrap up that troublesome little detail about the source of the gas. How had it moved from the engine to the cabin of the car?

When such a thing had happened before in other cases around the world, it was found to have been caused by leaks from damaged manifolds or exhaust gaskets, or cracks in the exhaust pipes that lined up with leaks in the shell of the vehicle interior.

But a routine check of this car left them with a puzzle. It was a recent model Mini Cooper, an expensive and well-maintained car. There were no problems with the exhaust system — and there were certainly no cracks or holes in the cabin.

The yellow and black car was in excellent shape: it looked new.

Police contacted Interpol who sent a message to the vehicle manufacturers in Europe to see if they could run their own tests and try to work out how things had gone wrong. Staff at BMW in Germany said they would report back in due time.


In the meantime, there was growing puzzlement among the Hong Kong detectives. They decided to try thinking out of the box.

There were no leaks in the car’s ventilation system.

If it really was impossible for the gas to have moved from the engine to the cabin in such a car, then it must have come from somewhere else. Perhaps they recalled the famous Sherlock Holmes quote: “When you have eliminated the impossible, whatever remains, however improbable, must be the truth.”

But where else could the gas have come from? There were no gas canisters in the car’s cabin or in the vehicle boot. Nor were there any other suspicious objects in the vehicle.

The list of items found in the car included a deflated grey yoga ball. For middle-aged people of this family’s wealth and status, this was not unusual: many people, women in particular, practiced yoga.

But an officer noticed that the yoga ball lacked a stopper. It must have fallen out. Yet it was not anywhere else in the car. Why would anyone separate an inflatable ball from its stopper?

It was odd, but once more, it was nothing but a detail.


The investigation continued quietly while the broken family struggled to get on with their lives.

Behind police station doors, a message was received from BMW in Germany. Specialists told the Hong Kong police that they were absolutely confident that the ventilation systems in the Mini Cooper would not and could not leak carbon monoxide into the main body of the car.

An officer made what seemed like a wild surmise — what if the gas had leaked out from the un-stoppered yoga ball?

The idea seemed a stretch. Yoga balls didn’t contain carbon monoxide. They would only contain such a thing if someone had deliberately pumped it inside. And if someone had done such a thing, it would indicate a deliberate act — and likely murder.

There were no known cases of “murder by yoga ball”. And why would anyone have done such a thing, anyway? The Khaws were the perfect happy family, right?


The official story was that the Khaws were a well-off family headed by a couple who had been happily married for 23 years.

But friends knew a different story. Khaw had had an affair with a former student. After it had come to light, his wife had refused to divorce him, and they lived in an unhappy and estranged state. Husband and wife had separate bedrooms and rarely spoke.

The wife, Wong Siew Fing, had been keeping a diary, and many of the entries dealt with self-reproach for the sad way her life had turned out. She wrote about her poor relations with her husband and her difficulties with her children.

“I didn’t listen when my husband tried to tell me he needed me,” she wrote in a diary entry from 2013, according to a report from South China Morning Post reporter Chris Lau. “I needed to… tell my children I loved them very much, that Mummy was going to be more responsible from now on, be a caring person rather than an impatient one.”


Still humoring their wild-sounding theory, police officers went to a trendy sports shop and bought a pair of yoga balls. While some officers talked to chemical suppliers and psychologists, others experimented with the balls, filling them with gas and seeing if they leaked.

They did. Gas poured out at a steady pace if the stopper was left off.

Officers also went to the medical school and talked to Khaw’s colleagues.

One of them revealed that Khaw had asked him to buy a tank of carbon monoxide for the purpose of conducting experiments on rabbits. Since the doctor was an anaesthetist, it was not a particularly unusual request for the department to buy a variety of gases. Yet this particular experiment did not seem to sit naturally with the rest of the department’s research.

The police interview with Khaw’s colleague, Dick Chow Ho-kiu, included one detail which caused officers’ eyes to widen. After one experiment on rabbits, Chow said that Khaw took some of the carbon monoxide – and pumped it into a pair of yoga balls. He then took the yoga balls home with him.


That was it.

Suddenly they had all three elements coming together: the toxic gas, the yoga ball, and the secretly unhappy Dr. Khaw, trapped in a loveless marriage.


By now, the police had filled in the details of their theory: Khaw had purchased carbon monoxide through the university medical school, pumped it into two yoga balls, and left one unstoppered in the back of his wife’s car, where it would have eventually permeated the air. Carbon monoxide was odourless and invisible — but deadly.

The most likely outcome of such a leak would have been for the driver to lose control and crash the vehicle, causing her own death and possibly the deaths of pedestrians or other road users.

It was potentially the perfect crime. The woman’s death would have been caused by the car crash while she was alone at the wheel. The gas would quietly dissipate.

If, by any chance, carbon monoxide was detected at the crash site, it would be assumed to have leaked from the car itself.

And, at the time of the woman’s death, the person responsible would be innocently giving a lecture far away in front of no less than 250 trustworthy eyewitnesses.

But by pulling the car over to the side of the road as soon as she felt unwell, Wong had protected other people. And the good condition in which she kept the car meant the easy assumptions of an engine leak had been made and dismissed.

Detectives wanted one more piece of the puzzle to make their case water-tight — a witness who had seen Dr. Khaw placing the toxic gas-filled yoga ball in the car. After interviewing dozens of people, it was clear that no such witness existed.

Yet they eventually found what they needed. The family’s Indonesian domestic helper, Siti Maesaroh, said she had seen her male employer bringing home a yoga ball from his workplace the night before the deaths.

On the last morning of the women’s lives, she had watched her female employer and Li Ling leaving the house and getting into the Mini Cooper: and they had definitely not been carrying the yoga ball.

Since it was later that day found in the back of the car, that meant someone else had put it there earlier. No one had been seen touching the ball except Dr. Khaw.


The case had taken a long time to come together. The police arrested and charged Khaw on September 11, 2017, more than two years after the deaths. He was taken first to the magistrate’s court and then to the High Court where he was charged with the murder of his wife and daughter.

The torrid story of the toxic gas and the yoga ball eventually came out in the legal hearings — as did some extra details.

The court heard that Dr. Khaw had casually told his daughter not to go out that day, the last day of her life. It’s hard to see this as anything but an admission that something very bad was going to happen to his wife when she got into her car and drove it onto the roads.

Then, during the trial, Dr. Khaw tried to blame his own child for the deaths, saying that she wanted the toxic gas to kill bugs and rodents, and was anyway suicidal.

But he was unconvincing, and the weight of the evidence against him was too heavy to ignore.

Verdict: Guilty. The doctor was sentenced to life in prison.

But it’s worth noting that police revealed during the trial that they had searched Dr. Khaw’s home – and in a drawer in his bedroom, a room he did not share with his wife, they found a tiny plastic item, easy to miss.

It was a stopper for the inflation valve of a yoga ball.

Detective work is all in the details.

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Pictures from public sources

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