Peter Madden from Belfast has told colleagues he expects to spend at least a week in Lima where Michaella McCollum Connolly, 20, from Dungannon, Co Tyrone, has been accused with Scots woman Melissa Reid, 19, of trying to leave the country with £1.5 million of cocaine in their luggage.
They were detained while trying to board a flight from the Peruvian capital to Spain last week.
The women claim they are victims of a violent gang who coerced them into carrying the drugs, and say they have resigned themselves to the likelihood that they face a lengthy prison term.
Police are waiting for a translator before officially questioning them, which is expected to happen in the next few days.
Mr Madden is one of Northern Ireland’s best-known lawyers and has been involved in a number of high profile cases.
A former colleague of murdered human rights solicitor Pat Finucane who was shot dead by loyalists in north Belfast in 1989, he was involved in the legal representation of three Irish republicans who were arrested in 2001 in Colombia for allegedly training members of FARC. They eventually returned to Ireland in 2005.
Melissa’s father William is understood to be flying out to Lima in a bid to be reunited with his daughter.
The teenager’s mother, Debra Reid, told the Scottish Daily Mail he will be with the former Lenzie Academy pupil on her 20th birthday tomorrow.
Meanwhile, the British Consulate in Ibiza has suggested international collaboration is needed to address the problem of drugs getting into the Mediterranean island.
Andrew Gwatkin, British Consul General for the Balearic Islands, told BBC Radio 1’s Newsbeat programme: “I think that the police are working extremely hard in Ibiza in very difficult circumstances.
“The vast majority (of drugs) are not produced in Ibiza though so international collaboration would be one of the positive and constructive ways we could tackle this problem.”
Ms Reid and Ms McCollum Connolly have claimed they were given the 24lb (11kg) of cocaine outside their hotel, the Hotel Colonial San Agustin in the capital Lima, the day before they were due to fly back to Spain.
The pair, who deny drug trafficking allegations, claim they were ordered at gunpoint by Colombian gangsters to smuggle the drugs out of Lima.
The two women had been working on the Spanish island of Ibiza, where they say they were snared by a drug cartel, robbed of their passports and phones and followed as they travelled on separate flights from Spain to Peru.
Once in South America, they say they were ordered to carry the cocaine hidden inside food packets.
Ms Reid and Ms McCollum Connolly could be held pre-charge for up to 30 days and then could spend up to three years in prison before a trial.
If convicted, they could face lengthy sentences in an overcrowded Peruvian prison where they will have to pay for everything, including food and bedding.