In an interview with former mayoral candidate John Catsimatidis on his Sunday morning radio show "Cats Round Table," Donovan said he assigned eight lawyers and 10 investigators, who work independently from the NYPD, to the case of Garner, 43, who died last month from an apparent chokehold while being arrested for selling untaxed cigarettes.
"We did a thorough investigation since July 17, the day Mr. Garner died, and we did an investigation independent of the police department," Donovan said on the show. "It's the biggest allocation of resources since I've taken office I've used on any matter."
While some, like Councilman Hakeem Jefferies, called for the federal government to take over the investigation because the prosecutor is perceived as too close to police, Donovan said several times that he's done a completely independent investigation. He said his philosophy is to investigate "without fear and without favor."
On Saturday, the Rev. Al Sharpton led a march from the spot where police placed Garner under arrest to Donovan's office, stopping in front of the 120th Precinct to call for justice against the officers who took Garner down.
Speaking on a separate radio show on Sunday, Mayor Bill de Blasio called the peaceful rally "something all New Yorkers should be proud of" in the wake of confrontations in Ferguson, MO.
"The march clearly was an example of police and protesters finding a way to get things done in a positive, democratic fashion," de Blasio said on COBA Radio. "It is something all New Yorkers should be proud of."
The NYPD said that no arrests were made during the march, and de Blasio said he hopes it will be the beginning of bridging the gap between the police department and the community.
"People are ready for that kind of unity," he said.
On his radio appearance, Donovan also spoke about his opinions on the "Broken Windows" policing policy — which targets quality of life issues to reduce major crimes — that has come under fire in the wake of Garner's death.
He said he's always has been a "fan" of prosecuting all laws in the books, and vowed to continue to prosecute low-level marijuana offenses even as some lawmakers are calling on DAs to stop.
"This is the first time I was asked by the state legislators not to enforce a law they created," Donovan said.
"I told them when they change the laws we'll enforce the laws as they're enacted, but for the time being if it's in our criminal statutes I took an oath to follow through and prosecute those charges."