Attorneys for former security guards with the military contractor Blackwater said Monday that the government has suppressed evidence favorable to defendants who are on trial in the killings in 2007 of 14 Iraqis in Nisoor Square in Baghdad.

U.S. Attorney Ronald Machen said that “a series of innocent oversights” led to the problem.

The defense team for the four former Blackwater guards said the suppressed evidence includes photographs of eight spent shell casings that would fit an AK-47 — the weapon of choice used by insurgents as well as Iraqi authorities. The attorneys said that insurgents fired on the Blackwater convoy and that the guards returned fire in self-defense.

A court filing by the lawyers said that an Army captain took the photographs at a bus stop several hundred feet from Nisoor Square and that they never saw the light of day until federal prosecutors turned them over on Wednesday.

“The government has suppressed, for seven years, evidence in its possession that is plainly exculpatory on the central disputed issue” in the case, the attorneys said in a court filing. “Had they possessed these photos, defendants would have made them a central focus during opening statements as evidence of incoming fire. Defendants also would have used this evidence to cross-examine at least four witnesses who have already testified” and who are not subject to being recalled, because they have returned to Iraq.

Defendants' Trial Exhibit DX2414 shows eight spent shell casings from the scene of the shootings of 14 Iraqis in Nisoor Square in Baghdad in 2007. (AP)

The defense attorneys are asking that they be allowed to explain to the jurors in the case why they are just now hearing about the new evidence. The lawyers also want the judge to tell the jurors that the government did not disclose the evidence before the trial, which began more than a month ago.

According to the court filing, then-Army Capt. Peter Decareau was one of the first Americans to arrive at the Nisoor Square crime scene. He took photos, including two of a group of eight AK-47 shells on the ground behind the bus stop. On Oct. 12, 2007, he gave the FBI a CD of the photos.

Based on Decareau’s testimony, federal prosecutors understood that Decareau did not observe any AK-47 shell casings on the scene, Machen wrote to the defense lawyers. In addition, prosecutors “incorrectly assumed” that a montage of Decareau’s photos contained all the photos from the disc he had provided to the FBI, Machen wrote.

The eight AK-47 shells have disappeared. Neither the State Department nor FBI agents recovered them.

“The physical evidence possessed by the FBI does not include the AK-47 shells photographed at the bus stop by Decareau,” the court filing states. “Decareau’s photographs are the only evidence of those AK-47 shells at the bus stop immediately after the incident.”

The court filing raised the possibility that Iraqi authorities had taken the shell casings.

“Notably, photographs taken Sept. 16, 2007, show many Iraqi officials at the bus stop,” the court papers said. “Decareau advised the FBI during his October 2007 interview that he observed” that an Iraqi army general took items from the scene.

The defense team said it would have used the photographs to rebut the government’s claim that no evidence of incoming fire was found and to point out to the jury how easy it was for evidence of hostile fire to disappear.

In a 2008 grand jury appearance, Decareau was questioned about some of the photos he had taken, but the exhibits did not include the two images of the AK-47 casings at the bus stop, according to the court filing.

In trial testimony Monday, the former team leader for the Blackwater convoy involved in the shootings made statements that might prove useful to the defense.

Team leader Jimmy Watson said he heard the incoming “pop” of what sounded like AK-47 rounds shortly before Nicholas Slatten, one of the four guards on trial, fired his weapon twice at the start of the violence.

Slatten is charged with first-degree murder in the death of the driver of a white Kia that was buried in gunfire from the Blackwater convoy.

In regard to the white vehicle, Watson said he considered it a “threat” because it was moving “pretty fast” toward the Blackwater convoy. Both the driver and his mother — who was also in the car — were killed.

— Associated Press