10/08/2017 7:57 AM AEST | Updated 10/08/2017 9:15 AM AEST

Cassie Sainsbury Will Face Trial As Judge Rejects Plea Bargain

She could now face 20 years in jail.

Accused drug mule Cassie Sainsbury is facing decades behind bars in Colombia after a judge rejected her plea deal in court on Thursday morning.

The 22-year-old Adelaide woman has been in a Colombian prison since her arrest in April at Bogota Airport, after police found 5.8 kilograms of cocaine concealed in her luggage.

She will now face a full criminal trial for trafficking the huge quantity of cocaine -- a charge which carries a maximum jail term of 30 years.

The South Australian shed tears as she was lead from court under heavy security in Bogota.

The plea deal would have reduced Sainsbury's sentence to a maximum of six years, with as little as three years with good behaviour, in exchange for her admitting guilt and naming people inside a drug smuggling ring.

The deal was on the verge of being accepted two weeks ago when Sainsbury told Judge Sergio Leon that she only took the drugs under threats to her mother and fiancé.

Judge Leon said the plea deal could not go ahead because Sainsbury had presented new evidence to the court and failed to accept full responsibility for her crime.

In a written statement presented to the court, Sainsbury claimed that she was threatened at gunpoint to put the drugs in her suitcase.

She also claimed drug traffickers told her she was being watched and could not leave Colombia, and sent her photos of her family and threatened to harm them.

Sainsbury's mother Lisa Evans and fiancé Scott Broadbridge, who were in court to hear the judge's decision, had pressured her to accept the plea deal but she had refused, her lawyer Orlando Herran said.

Shortly before going into court on Thursday, Herran told reporters Sainsbury was sticking to her story that she was blackmailed into carrying the drugs.

"At the moment, we only have Cassandra's word about the threat. Cassandra doesn't have the personal resources for a private investigator to prove the threat," he said outside court.

Handout . / Reuters
Cassie was arrested on April 12 at Bogota international airport after security found 5.8kg of cocaine concealed inside headphones in her luggage.

In Colombia, the maximum prison sentence for trafficking over 2 kilograms of cocaine is 30 years.

Herran had earlier said that if found guilty Sainsbury would serve between eight and 20 years, but according to News Corp, a source from the prosecution said Thursday she was facing between 21 and 30 years imprisonment.

Australian consular staff were on hand in court to provide assistance, Foreign Affairs Minister Julie Bishop has confirmed.

Sainsbury will remain inside the overcrowded El Buen Pastor women's prison in Bogota until her trial in several months' time.