Setback for Obama as first former Guantánamo detainee to be tried in civilian court is convicted on just one of 285 charges

Barack Obama's plans to try accused terrorists in civilian courts experienced a major setback last night when the first former Guantánamo detainee to be tried in one was convicted on just one of 285 charges over the 1998 attack on US embassies in East Africa which killed 224 people.

Ahmed Khalfan Ghailani, a 36-year-old Tanzanian, was found guilty of conspiracy to destroy US government buildings and property for helping an al-Qaida cell to buy a lorry and bomb parts in the attacks on the American embassies in Kenya and Dar-es-Salaam. But a US federal jury acquitted him of all the more serious charges of murder and conspiracy.

Ghailani faces 20 years to life in prison when he is sentenced in January. He had already been told that even if he was acquitted on all counts he would not be freed so long as America remains "at war" with al-Qaida.

However, the verdict is an embarrassment for US prosecutors who maintained that Ghailani played an important logistical role in the attacks but were unable to persuade a jury which showed signs of serious disagreement during deliberations, with one juror asking to be excused because of differences with other jurors. The judge, Lewis Kaplan, refused.

The failure to convict Ghailani on the more serious charges is also a blow to Obama's attempts to persuade a sceptical Congress and security establishment that civilian trials are better than the widely condemned military tribunals held at the Guantánamo detention centre. The trial was considered a test run.

The administration plans to put Khalid Shaikh Mohammed, who is accused of masterminding the September 11 2001 attacks, on trial before a civilian court although it is now wavering over whether it should be in New York. At least four other Guantánamo detainees are also earmarked for civilian trials.

Prosecutors in the New York court faced greater constraints than at the Guantánamo trials. Judge Kaplan refused to admit some evidence collected while Ghailani was held after being captured in Pakistan six years ago and interrogated by the CIA at a secret location before being moved to Guantánamo Bay. Ghailani's lawyers said he was tortured by the CIA.

Prosecutors decided against using what they said were Ghailani's confessions made during interrogation.

The judge refused to allow the prosecution to put a witness on the stand. Hussein Abebe was to testify that he sold Ghailani the explosives used to attack the US embassy in Dar-es-Salaam. But other witnesses testified as to how Ghailani bought gas tanks used in one of the bombs.

His lawyers contended that he was duped into assisting with the bombings by al-Qaida operatives.

"Call him a fall guy. Call him a pawn. But don't call him guilty," said Ghailani's lawyer, Peter Quijano.

American officials assert that Ghailani was closely tied to the terror group. He fled to Pakistan on a one-way ticket under an alias the day before the bombings and then spent time in Afghanistan as a cook and bodyguard for Osama bin Laden.

They say that he later became a document forger for al-Qaida.