Two Indonesian men, Imran Hafid and La Bahrudin La Bahrudin, were released from the Alexander Maconochie Centre into the custody of immigration officials in recent months after spending about a year locked up in detention centres and prison awaiting trial. Both are understood either to be on their way home or already deported.

Another three accused smugglers remain locked up in the AMC, and on Thursday the trio were committed to stand trial in the ACT Supreme Court.

But Canberra lawyers have already asked either the courts or prosecutors to end the cases against their clients, arguing they have got no reasonable prospects of conviction.

They have warned systemic delays plaguing the territory's higher court mean their clients will spend up to two years behind bars on remand, with jury trials currently being listed for mid-2014.

Mr La Bahrudin, 50, had been in custody since November last year, when the navy boarded the SIEV 279 about 15 nautical miles from Christmas Island. There were 121 passengers on board and, according to court documents, several identified Mr La Bahrudin as a crew member.

The same month, SIEV 284 left Indonesia carrying 19 passengers and allegedly five crew members. It was intercepted about three nautical miles inside Australian waters.

All of the Afghani men on board later identified 25-year-old Mr Hafid as being on board, and some allegedly saw him steering the boat.

Mr La Bahrudin and Mr Hafid were brought to Canberra in March under a national prosecution sharing agreement. They pleaded not guilty to charges of aggravated people smuggling carrying a mandatory minimum jail term.

Those charges were downgraded in September when Attorney-General Nicola Roxon directed prosecutors to lay less serious charges after an outcry from interstate judges.

The entire cases against Mr La Bahrudin and Mr Hafid were abandoned in October and last month against a backdrop of aborted prosecutions in other jurisdictions.

The trend has been most marked in Victoria, where the state's legal aid commission said in September about half the jurisdiction's 66 people-smuggling prosecutions had been discontinued.

The office of the Commonwealth Director of Public Prosecutions could not be reached for comment on Friday, and the reasons for dropping the two Canberra cases are unclear.

But many of the discontinuations in the southern state came after a Victorian Court of Appeal ruling in June that said in order to prove a people-smuggling charge, the Crown had to show an accused knew Australia was their destination.

The lawyer for one of the ACT's three remaining accused smugglers, Marcus Hassall, on Thursday unsuccessfully tried to have the case against his client Toni Kaubulan thrown out at the committal stage, citing the Victorian decision. Kaubulan is accused of being part of a crew who picked up 21 Bangladeshi and Burmese asylum seekers from a deserted island between Indonesia and the Ashmore Islands after their first boat started breaking up.

Solicitors representing the other two men told The Canberra Times on Sunday they had written or would write to the Commonwealth DPP urging them to let their clients go.

Lawyer Craig Lynch said: ''I wrote representations highlighting the weaker case against my client, and I also highlighted the delay in the proceedings and whether it's in the public interest to continue with charging someone when, if he was found guilty, the sentence imposed would be less than what he's already been in custody for.''

Paul Edmonds, whose client Rakiba Rakiba is accused of being in charge of the voyage and telling passengers he was ''a human compass'', said the Victorian case, necessity and the likely delay in getting to trial were ''live issues''.