NEW YORK The defence in Aafia Siddiqui's case brought in a forensic expert on Wednesday who testified that there was no evidence that a high-velocity M-4 gun was fired during a 2008 confrontation at an Afghan police station in Ghazni as claimed by the prosecutors.

The Pakistani neuroscientist is accused of attempted murder of US soldiers and FBI agents who were seeking to interview her at a US base in Ghazni. No one was hit in that incident, but Dr Aafia was wounded when a US Army officer shot her.

William Tobin, a former Nasa employee, who testified as a forensic expert, said that in his opinion a photograph showing two holes in the wall were, with “scientific certainty”, not consistent with either a high velocity or low velocity bullet hole. He said they were simply “not bullet holes”.

“SS09 bullets would have caused substantially more damage not only to the wall but also to the ceiling,” he testified.

Mr Tobin also said that the firing of an M4 would be such a “devastating event from a material standpoint that there should be a lot of evidence at the scene”.

According to his testimony, FBI officials are trained in gathering even the smallest fragments of evidence, but in the description of the incident given by the government there should have been even large fragments. Despite the fact that FBI officials were present at the shooting, no evidence of M4 shots were collected, neither large fragments nor small ones. Furthermore, no M4 casings, bullets, or residue were found anywhere in the room.

Last week FBI ballistics expert Carlo Rosati, who appeared as a government witness, made a similar statement. According to him, it could not be said with certainty that any shots were fired from the M-4 rifle. The only bullets fired at the scene were from the M-9 pistol that a US Army officer used to hit Dr Aafia.