The shock decision came after Sainsbury told the court she had agreed to smuggle drugs only because her family and fiance had been threatened.
Those comments may endanger the deal the 22-year-old had struck with prosecutors to serve just six years instead of at least 20 in return for information on the ring.
Sainsbury has told the court in Bogota on Thursday morning that she “didn’t want to take any package anywhere” but did so under coercion.
“I was told that my family and partner would be killed,” she said when asked what would happen if she didn’t agree.
This April 12, 2017 photo released by Colombia’s National Police press shows Australian Cassandra Sainsbury in handcuffs after she was arrested.AAP
Judge Leon told the court on Sainsbury’s explanation raises questions about the the legality of the deal. Another date will be set for the hearing.
Sainsbury was caught at Bogota’s international airport in April, trying to smuggle 5.8 kilograms of cocaine inside 18 separate packages of headphones.
She has been held in a Bogota prison since her arrest, with her case attracting huge attention in Australia.
Her mother Lisa Evans and fiance Scott Broadbridge were in Bogota to support her during the sentencing hearing on Thursday morning Australian time.
Sainsbury’s sister on Wednesday told Channel 7 in Adelaide the plea deal was the best outcome they could have hoped for.
But Kahla Sainsbury said her sister’s life would never be the same, even after just a few years in prison.
0:00 Dutton comments on Sainsbury’s legal costs Share Dutton comments on Sainsbury’s legal costs
“I don’t think there’s much she can do when she comes back home. It’s going to be hard for her to get a job. It’s going to be hard for her to do anything,” she said.
“Because she’s going to be labelled as ‘Cocaine Cassie’.”
Immigration Minister Peter Dutton said the case served as another warning to Australians travelling overseas.
“People need to abide by the laws of that country. If not, they will face serious consequences,” he told Seven on Thursday.
The government provided consular assistance to Sainsbury but did not fund her legal case, Mr Dutton said.