In April, Adelaide woman Cassie Sainsbury was just another young blonde traveller checking in for a flight at the El Dorado airport in Bogota, Colombia.

Security footage showed her in tracksuit pants, chatting easily with an airline staffer. Her life was minutes away from changing forever.

As the bag went through checks, an X-ray machine detected 5.8 kilograms of cocaine stashed in 18 packages in sets of headphones. Sainsbury was arrested, charged and locked up in one of South America’s toughest prisons.

But even away from the public gaze, the drug mule became an instant household name, notorious as ‘Cocaine Cassie’. Heading into 2018, she’s the highest-profile Australian now in jail overseas.

What made Sainsbury’s story more sensational than that of other imprisoned Aussies, turning her life from a personal tragedy into a public circus?

Firstly, she let the media in, taking part in a 60 Minutes “exclusive” interview during which her shot at gaining sympathy or salvaging her reputation – if that was her goal – was hijacked when she was accused of telling “porky pies” and of smiling “inappropriately.” Another news outlet pronounced her story “was full of holes”.

That story was complicated, and Sainsbury came up with several versions. Initially she said she was innocent. Then she copped to accepting a $10,000 job offer as an international “documents” courier, although it seemed “a bit suss”.

Then she said when she was forced by a drug syndicate to carry the drugs after her family was threatened via WhatsApp on her mobile. The proof was on her mobile phone, Sainsbury said, but she couldn’t remember her security code: “I’ve been trying.”

The changing yarn – a failed gym enterprise, a cleaning company, unpaid debts – intrigued the public at home. Soon, grubby claims emerged, which did Sainsbury no favours: she denied allegations that before her Colombia run she lived a “double life”, commuting from Adelaide to work as a prostitute in Sydney brothel Club 22. Funded by a commercial TV network, her mother and sister flew to Bogota where they stood outside El Buen Pastor prison, with cameras rolling, and absurdly yelled greetings at Cassie.

Cassandra Sainsbury was sentenced in November o six years jail, but could be out earlier.

Her fiancé Scott Broadbridge also made a Colombia visit, and did a TV interview, saying he would wait 20 years for Cassie, even though “everything is telling me I should just walk away”. An uncle also piped up. Armchair judges were delighted.

After various hearings and pleas, a judge accepted a plea deal and Sainsbury was sentenced in November to six years prison and a fine of nearly $131,000 for trafficking cocaine. Her lawyers say she should be out in three years with good behaviour. Broadbridge is flagging the idea of a jail wedding.

And under the whole sad soap opera is Cassie Sainsbury, one ordinary woman whose case shone a light on the plight of hundreds of foreign drug mules in Colombian prisons. One ordinary woman who was the year’s most headturning cautionary tale.

From A-list stars to politicians and athletes, we’ve named the 13 Australians who made headlines and sparked conversations – both heated and admiring – across the nation in 2017. Some covered themselves in glory. Some created controversy. Some made reputations, others lost them. From the cricket arena to the same sex marriage battlefield, regardless of whether they were beloved or booed, their personal and professional wins and downfalls had us talking over dinner tables and media channels.