Wichita ? An attorney for a Kansas man accused of committing atrocities during the Rwandan genocide says the Justice Department decided to drop charges after prosecutors were threatened with sanctions for withholding evidence.

Attorney Melanie Morgan says it was a serious mistake that she would not have expected experienced prosecutors to make.

The defense offered its glimpse into the behind-the-scenes negotiations that brought an end to the costly prosecution touted as the first in the nation requiring proof of genocide after a judge tossed out all charges against Lazare Kobagaya.

Prosecutors asked a judge on Thursday to overturn the verdict and dismiss the entire indictment after spending more than $1 million to convict the 84-year-old Burundian immigrant of visa fraud. Prosecutors say the nondisclosure was a mistake.