When passengers boarded the boat, he was told it was for a sightseeing tour of the surrounding islands. The next thing he knew, he told his lawyers, their boat was picked up by an Australian navy ship with guns and he was put in detention and then jail.

''The people smugglers simply get naive people, and the youths fall into that category,'' said Faisal's Brisbane lawyer, David Svoboda.

''These kids sit in villages with no work. Recruiters walk into the village offering $500. They tell them they will be met by a ship to pick these people up at their destination. When a ship rolls in and it's full of cannons, it's really surprising. These kids are genuinely surprised it's the Australian navy.''

The Australian Federal Police did not believe that Faisal was 16. They decided to give him a widely discredited wrist X-ray test that estimated his age to be 19. The AFP charged Faisal with people smuggling and he was put in the Arthur Gorrie maximum-security jail in Brisbane, which houses paedophiles among its inmates.

Eight months later, the charges have been withdrawn after Svoboda flew to Indonesia to gather proof of Faisal's age.

Faisal's case was one of two due to go to court last Wednesday. But the charges were dropped because the Commonwealth Director of Public Prosecutions could not prove the accused were adults. The boys, both from Kupang, will now be sent back to their families.

The cases highlight the plight of dozens of Indonesians who say they are children and who are incarcerated in adult jails around Australia.

The government told Greens senator Sarah Hanson-Young in Parliament last week that there were 25 people in custody claiming to be under age. The AFP said in a statement on Friday that there were 34 cases of Indonesian nationals in jail in which age was being disputed. The Indonesian consulate-general in Sydney believes there are about 50.

Whatever the correct number, the jailings have sparked a growing outrage among lawyers, diplomats, politicians and human rights activists in Australia and Indonesia.

This is particularly so when measured against Indonesia's treatment of the 14-year-old Australian boy from Lake Macquarie, NSW, who appeared in court in Bali on Thursday, accompanied by his father, and pleaded for leniency on drug charges.

''We have one boy over there who is getting KFC sent in and is in a room [near] his parents,'' Svoboda said. ''These kids aren't getting too much nasi goreng delivered to Arthur Gorrie [prison], are they?''

The jailings in Australia have angered Indonesian lawyers and activists who staged a little-reported protest outside the Australian embassy in Jakarta two weeks ago, calling for the federal government to release the teenagers and send them home.

Indonesian diplomats in Australia are so concerned they have enlisted the help of a barrister, Mark Plunkett, to investigate the cases.

They also want the government to put in place a co-ordinated, consistent plan to establish the proper ages of the teenagers.

Plunkett said it would involve visits to families and villages in Indonesia, where birth documentation is rare, to obtain credible information about their ages.

''They don't make any effort to check whether they are children or not,'' Plunkett said. ''They rely on junk science and don't even bother to call their parents.

''Police don't even do the most basic investigation 101: find mum and dad,'' he said.

The AFP, however, said in a statement that it did seek the help of the Indonesian National Police and other Indonesian authorities to gather as much information as possible for age determination inquiries.

Plunkett helped secure the release of three teenagers in July. They had been accused of lying about their ages. He travelled to Indonesia with Indonesian expert Tony Sheldon to gather affidavits and evidence from their village chief about their age.

The jailing of the boys was ''despicable'' and a breach of the United Nations Convention on the Rights of the Child, he said.

He also said the imprisoning of the children could be ''actionable''. The boys had been brought into court in manacles and had been subjected to cavity searches when put into Arthur Gorrie prison.

In that case, the AFP had ignored advice from the Immigration Department and documentary evidence, in the form of birth extracts, to pursue prosecutions against the three teenagers from Roti Island - Ose Lani, who said he was 15, and John Ndollu and Ako Lani, who said they were 16.

They had worked as deck hands and cooks on a boat that arrived at Ashmore Reef last year. They spent months in Arthur Gorrie jail before being released when the court accepted they were children.

Other cases include that of Ardi, an illiterate orphan boy from the island of Lombok who says he was 16 when he was recruited.

Recruiters who turned up in his coastal village in February last year had offered him $550 to work as a deckhand on a boat taking foreigners around the islands.

Ardi's boat, full of Afghan asylum seekers, was picked up by an Australian customs vessel off Western Australia the next month. He spent 10 months in immigration detention without charge before being sent to the Arthur Gorrie adult jail in Brisbane on criminal remand. He had no form of identification and no way to prove his age.

His lawyer, also David Svoboda, made three trips to Indonesia to get the necessary papers. Eventually the charges were dropped and Ardi was sent home after 19 months behind bars.

Another boy, Mukhtar, says he was 15 when he was recruited from Roti. He was paid $400 to act as crew, and in late 2009 he was caught off Christmas Island. He was held for eight months in detention and then transferred to the maximum-security Hakea Prison in Perth, where other inmates included killers and paedophiles.

After a year and 11 months, a Perth court dismissed charges of people smuggling and he was sent home last month.

Federal government policy is that children acting as crew on boats carrying asylum seekers should not be charged but sent home. Adult crew members are charged with people smuggling offences and face five-year mandatory jail sentences.

An AFP spokesman said there ''is an onus on the AFP to charge and bring before the courts all adults involved in people-smuggling endeavours.

''Where all available information indicates the person is a minor, and there are no exceptional circumstances, the person is returned to their country of origin,'' the spokesman said.

''Statistics since September 2008 indicate that about one in three (38 of 107) of those people who undergo an age determination test are returned to their country of origin.

Plunkett says if there is any doubt at all, the crew members should be sent home.

But many of the Indonesian crew who say they are aged 14 to 17 end up facing people smuggling charges as adults because the AFP has continued to use the widely discredited Greulich and Pyle wrist X-ray test, despite being warned by international experts that it is unethical and unreliable, and has been banned in Britain.

The AFP has argued that it is the only prescribed method under the law to check a person's age.

However, federal police use of the method has not gone well. The Commonwealth prosecutor's office has confirmed that 32 cases, including the two last week, have been dropped because the test could not be relied on in court.

But one of the cases that has not been dropped is that of Sam (not his real name), who says he was 15 when he arrived as a cook on an asylum seeker boat in April last year.

His mother and sister, who spoke to a Perth journalist from their home on the outskirts of Solo, in central Java, insist he was born in April 1995.

The AFP did not believe him and gave him the wrist X-ray, which put his age at over 18. He was charged and has been in Perth's Hakea jail ever since, awaiting trial on people smuggling charges.

Catherine Branson, QC, president of the Australian Human Rights Commission, has raised serious concerns about the processes used for determining age in criminal proceedings, particularly wrist X-rays,

''The use of wrist X-rays for determining age may have led to errors in age determination, with the result that some children may have been incarcerated in adult prisons,'' she said.

''The commission has recently received notifications from 11 Indonesian nationals detained in adult prisons who claim to be children.''

Branson said it forwarded the details to the Attorney-General's Department and was waiting for a response. The commission is considering what further action it might be able to take.

A spokeswoman for Home Affairs Minister Brendan O'Connor said the government had already asked the AFP to improve its processes for age determination, including offering dental X-rays, more thorough attempts to get information about people from their homes and families, and additional interview techniques.

The improved processes are too late for Faisal Aryad, who has already spent eight months in detention and jail.

However, it is hoped this week the authorities will finally fly him home to his village in Kupang to be reunited with his anxious mother and grandmother.