Downey also mentions oenologist Frankie Zhao, who claims 70 per cent of Chateau Lafite Rothschild in China is fake.

Part of the problem is China’s high import duty on wine, which results in some collectors hiring what Downey calls “coyotes” to bring in bottles through non-taxable channels – but these importers could also be switching the real ones for fakes.

“This would not happen in Europe, because they have traditionally collected generationally,” Downey says. “There is a family collection and children grow up around wine, and they learn about wine with and from the family. People have relationships with wine merchants built on trust, so by the time someone becomes a wine collector in their 30s or 40s, they have a lifetime of knowledge behind them and long-standing relationships with wine merchants or wine producers.”

The problem for buyers in Hong Kong and China is similar to the situation in the US, where they has been no generational collecting.

“Those who started wine collecting got their knowledge from reading [wine critic] Robert Parker and the internet; they had way more money than knowledge, and way more ego than sense,” she says.

With no relationship between buyer and seller, she says, provenance is no longer important to these buyers, who care only about the price.

This, in turn, has made it easier for wine counterfeiters to profit from selling fake wines, because new collectors just wanted the famous names.

Downey’s interest in wine was piqued when she was a first-year student at Boston University, where she studied hospitality. She later studied for advanced Master Sommelier certification and moved to New York, where she managed fine-dining restaurants.

With a sophisticated wine palate, obsessive compulsive disorder and a good memory, Downey found it relatively easy to detect fakes.

Counterfeits first came to her attention when she worked at Morrell in 2000 as an auction specialist. She knew she was handling a fake bottle of Petrus because it was too light, and nearly flew out of her hand. “No one was teaching me, but I knew it wasn’t right.”

There was no course on spotting fakes when Downey entered the trade, so she began doing her own research. She learned from a paper expert at New York’s Metropolitan Museum of Art how paper ages, and techniques to make paper look old. She also asked her cousin, a glass specialist, about the history of glass and how it changes with age.

By the time she began working at wine auctioneer Zachys in 2002, she’d become known for detecting fakes.

During her recent seminar in Hong Kong, Downey explained that wine fraud isn’t limited to counterfeiting; it also includes selling fake wines online, stealing wine in transit (from restaurants and from storage facilities), and claiming insurance on it.

Although Downey’s main business is appraising and enhancing clients’ wine collections, she also authenticates wines.

“It’s about logic, having a good eye, and patience. You have to be willing to say, ‘I can’t make a call on it now. I need to go back and research it.’ You can’t be too quick to judge. Jumping to conclusions won’t get you anywhere,” she says.

Like a detective, Downey carries around her authentication tools: a magnifying glass, jeweller’s loupe, torches (including one that emits a blue light) and box cutters.

She points out that counterfeiters are not all familiar with the history of the chateaux, and this can be a giveaway. For example, the label on a 1923 wine bottle from France would not contain the words “appellation d’origine controlée” because the guarantee of origin and quality was not instituted until 1935. It’s also important to know about bottle sizes and shapes for the different chateaux, the kind of glass used, capsules and corks.

Bottles should be consistent: if the label looks old but the capsule (the foil or metal that covers the cork) is new – like a bottle of 1949 Musigny that had a recycling symbol on it – then it’s obviously dodgy. If the letters on the label are either too close together or far apart, it has been printed on a computer. If they are printed by the chateau, it is usually done with a plate press and the letters never shift.

On a bottle of Petrus, the 3D red lettering is always sharp and detailed, even on older bottles. On fake ones, the red ink lines become a solid patch. Downey also jokes that if the picture of St Peter on the label looks more like Osama bin Laden, it’s probably not real Petrus.

She uses the torch with blue light to check the paper label. Paper made for wine labels from 1957 onwards become fluorescent in the blue light because of a certain chemical used. So bottles that look old but have labels that glow in blue light are questionable. Sometimes counterfeiters use labels made of recycled paper, which wine producers don’t use.

Other clues can be found in the corks. For example, those used for Bordeaux wines are 55mm or longer. Glue on the capsule is also a bad sign; glue isn’t used by winemakers.

Downey says sediment in bottles is difficult for counterfeiters to fake, and something isn’t right if the sediment shines brightly like glitter when light is shone on it.

Still, it’s not easy for novices – or even many of those involved in wine – to spot a fake, she says.

“There are [wine dealers] who have good intentions, but don’t have the education. But in this game you need to know what you’re doing.”

Ironically, she says, it’s sommeliers who tend to know the least about counterfeit wines because they don’t spend time with old wines, or working in wine shops or auction houses.

And while some producers of fine wine are trying their best to thwart counterfeiters by changing labels or adding holograms, others don’t have the resources to answer buyers’ queries regarding if they have bought the real thing.

One seminar attendee, Eric Desgouttes of Kerry Wines, admits many people in the local wine industry don’t have enough knowledge. “Hong Kong is not making fakes, but we source wines from around the world. Maybe we should be asking more questions.”

During his time in Hong Kong, Desgouttes admits, he has unknowingly bought and tried several fake wines, and says collectors and buyers should speak out more.

The Hong Kong Customs and Excise Department says it has a team of 12 focused on investigating suspected counterfeit wines with contacts in the wine industry locally and in China.

“We are aware of certain comments from some purported wine consultants on possible counterfeit wine problems in the market. However, no material detail for follow-up could be provided upon enquiry,” the department says.

Since the team was formed in 2008 – when Hong Kong axed the import tax on wines – only one person has been charged in relation to counterfeit wine. A court found the defendant not guilty.