Evidence that prosecutors improperly kept from grand juries in a Maricopa County murder case has led to the acquittals and dismissals of all charges in the case, which went to trial earlier this month.

Michael Kiefer, who wrote a terrific four-part series on prosecutorial misconduct in Arizona last year, reported this morning for the Arizona Republic that all remaining charges in the case of Jonathon Cobian and John Mena were dismissed by Maricopa County Attorney Bill Montgomery’s office yesterday due to a lack of evidence.

The Maricopa County Attorney’s Office has been at the center of controversy over prosecutorial misconduct in Arizona in recent years, with the Debra Milke case and other death penalty cases in particular suggesting a pattern of withholding exculpatory evidence.

911 calls that supported Cobian and Mena’s claims that they killed members of a gang in self-defense were not played for the grand juries that indicted them in 2007, 2008 and 2009, leading to all three sets of indictments being thrown out. Kiefer reports,

A former prosecutor on the case was found to have committed prosecutorial misconduct for ignoring judges’ orders to inform three different grand juries that 911 tapes made at the time of the attacks were potentially exculpatory and that the defense attorneys wanted them to listen to them.

Those calls ultimately saved the brothers from conviction.

Assistant County Attorney Eric Basta went so far as to refile the brothers’ case so that it might be heard by a different judge, but was unsuccessful. According to Kiefer, one judge who presided over the case found Basta to have committed prosecutorial misconduct:

Superior Court Judge George Foster threw out the indictments and wrote, “The court finds such an argument to be disingenuous. The 911 tapes contain evidence that is clearly exculpatory and the prosecutor should have informed the grand jury of the exculpatory evidence and the defendant’s request that the grand jury hear the tapes.”

When the case finally went to trial, the jury found the brothers not guilty of some of the alleged murder and assault charges, but were unable to agree on two counts of murder and other charges. The charges on which the jury hung were those dismissed yesterday by the Maricopa County Attorney.