Story highlights

NEW: The attorney for Spec. Michael Wagnon says there was new evidence

"The United States dismissed the charges in the interest of justice," the military says

Wagnon, 31, was charged with the February 2010 killing of an Afghan civilian

Wagnon was one of 12 Army soldier initially charged in the case

CNN  — 

Charges have been dismissed against an Army soldier accused in what prosecutors described as a conspiracy to kill Afghan civilians for sport and then cover it up, the military said Friday.

The charges against Spec. Michael S. Wagnon were dismissed without prejudice, according to a statement released by the military at Joint Base Lewis-McChord in Washington.

“The United States dismissed the charges in the interest of justice,” the statement said.

While the U.S. military did not say why the charges were dismissed, Wagnon’s attorney, Colby Vokey, believes it was because new evidence was uncovered as well as problems identified with the testimony of a key prosecution witness – a fellow soldier.

“The evidence proving his innocence was overwhelming,” Vokey said.

By dismissing the case without prejudice, military prosecutors could file charges against Wagnon at a later date, according to the attorney.

Wagnon, 31, was charged with the February 2010 unlawful killing of an Afghan civilian.

The Las Vegas resident was the last of 12 soldiers, all members of the Washington-based 5th Stryker Combat Brigade, to be tried in a case that strained U.S. relations with Afghanistan after allegations emerged that some of the soldiers allegedly posed with dead Afghans and collected souvenirs from the killings.

Military prosecutors have said the killing-for-sport plan was hatched by Staff Sgt. Calvin R. Gibbs, 25, of Billings, Montana, and that the group based in the volatile Kandahar province in southern Afghanistan began killing civilians in January 2010.

The case drew international outrage when Der Spiegel, a German news magazine, published photos that showed two of the soldiers – Spec. Jeremy Morlock and Pfc. Andrew Holmes – posing over dead bodies of Afghans.

In November, Gibbs was sentenced to life in military prison with eligibility for parole in 10 years.

A military court-martial found Gibbs guilty of murdering three Afghan civilians, illegally cutting off pieces of their corpses to keep as “souvenirs” and planting weapons to make the men appear as if they were Taliban fighters killed in legitimate firefights.

Five soldiers, including Morlock and Holmes, were convicted for various roles in the conspiracy. Six other soldiers, including one who posed for photos with a dead Afghan, accepted plea deals, the military has said.

As part of a deal, Morlock agreed to testify against the other soldiers and was sentenced to 24 years in prison for his role in the Afghan killings.

But Vokey maintains there were problems with Morlock’s testimony against Wagnon, who has proclaimed his innocence since he was charged.

Morlock, according to previous testimony, admitted to frequent drug use and problems with memory loss.

Vokey also raised questions about Morlock’s version of events, saying he did not initially identify Wagnon as one of the soldiers involved. That only came after Morlock reached a plea deal, he said.

When Wagnon received news the charges were dismissed, he was overwhelmed.

“He said ‘Are you sure they really did that? It isn’t really a dream?,’” Vokey said.

Wagnon will remain in the military, serving at Joint Base Lewis-McChord, he said.

CNN’s Tina Burnside contributed to this report.