In late 2008, Darby acknowledged in an open letter that he had acted as an FBI informant in infiltrating protest groups before the 2008 Republican National Convention, held in Saint Paul, Minnesota.

[1][8] Following the extensive damage in New Orleans by Hurricane Katrina in 2005, Darby was among numerous emergency medical personnel who went there in the first weeks to help the residents.

He helped organize volunteers from across the country over the ensuing weeks and months, as CGR set up emergency clinics, distribution centers, and other aid.

He also expressed regret at all the women who left Common Ground Relief due to Darby's behavior during his time at the organization, including claims that he sexually assaulted female organizers[11] Darby started working as an FBI informant in November 2007, to infiltrate groups planning protests at the 2008 Republican National Convention in St. Paul, Minnesota.

[13] Two activists from Texas, David McKay and Bradley Crowder, purchased materials for and constructed firebombs (Molotov cocktails) that they appear to have planned to use against state-owned vehicles.

[15] In a December 2008 open letter to his former fellow community organizers and activists, Darby acknowledged having worked as an informant for the FBI.

[14] Jury interviews indicated that much of their discussion had concerned assessing the veracity of defendant McKay and witness Darby (the former claiming entrapment, the latter denying).

[19] Critics have suggested that both McKay and Crowder remained firm in their initial account of events, and that additional documentary evidence supported them.

McKay's decision to take the plea deal was based on his awareness that 90% of federal cases result in convictions, and he was at risk of being sentenced to decades in prison if found guilty.