The lawyer for drug trafficking suspect Michaela McCollum said both of the women being held for drug offences knew "as soon as they arrived at the airport" at Lima that the police knew they were carrying something in their cases.
Speaking ahead of their court appearance Peter Madden said the women think they may have been a decoy for a larger shipment of drugs.
"When they arrived at the airport, they have told the police this, they knew that the police knew what was going on. So they were immediately arrested."
Melissa Reid and Michaela McCollum appeared in court in Lima, but it is unclear whether they have been charged, their lawyer said.
Two women accused of smuggling 12kg of cocaine into Peru could face up to three years in custody and a maximum of 25 years in prison.
A British woman accused of drug trafficking in Peru said she and her friend "were not smuggling for money, we were smuggling for our lives."