Pou and two nurses were arrested last summer after Attorney General Charles Foti's investigation concluded they gave four patients a "lethal cocktail" at Memorial Medical Center amid the chaotic conditions that followed the August 2005 storm.
Foti said the doctor and nurses had determined the patients were too ill to be moved.
Pou has emphatically denied murdering anyone, and lawyers for the three have said they acted heroically by staying to treat patients rather than evacuating.
"I did not murder those patients," Pou told CBS' "60 Minutes" last fall. "I've spent my entire life taking care of patients. I have no history of doing anything other than good for my patients."
In a December 2005 interview, she told WBRZ-TV of Baton Rouge: "There were some patients there who were critically ill who, regardless of the storm, had the orders of do not resuscitate. In other words, if they died, to allow them to die naturally, and to not use heroic methods to resuscitate them."
"We all did everything in our power to give the best treatment that we could to the patients in the hospital to make them comfortable," Pou said told the station.
The Orleans Parish grand jury had been investigating the allegations since March.
Charges against the nurses, Lori Budo and Cheri Landry, were dropped after they were compelled to testify last month before the grand jury under legal guidelines that kept their testimony from being used against them.
Assistant District Attorney Michael Morales had asked the grand jurors to return one charge of second-degree murder and nine of murder conspiracy against Pou.
He declined to comment after the judge read their decisions rejecting each charge.
When the levees broke in New Orleans following the hurricane's landfall, 80 percent of the city flooded. The lower level Memorial Medical Center was under 10 feet of water, and electricity was out across the city. Inside the hospital, the temperature topped 100 degrees.
At least 34 people died at Memorial, many from dehydration during the four-day wait for rescuers to evacuate them. In the "60 Minutes" interview, Pou acknowledged administering drugs to relieve pain but stressed: "Anytime you provide pain medicine to anybody, there is a risk. But as I said, my role is to help them through the pain."
Other doctors who were there described the situation as resembling a MASH unit during wartime rather than an urban American hospital.
"It was stifling. We were hoisting patients floor to floor on the backs of strong young men. It was as bad as you can imagine," Dr. Gregory Vorhoff, who stayed throughout the storm and eventually hitched a ride on a boat to seek help, told The Associated Press after Pou was arrested.
Pou, whose specialty is eye, ear, nose and throat surgery, gave up her private practice after she was arrested and has been teaching at LSU medical school in Baton Rouge.
The families of people who died at Memorial in the days after Katrina can still sue Pou.
Assistant Attorney General Julie Cullen, who sat in on the grand jury hearings, said investigators in her office still consider the deaths to be homicides.
Asked what the grand jury's decision does for Pou's reputation, she said, "I guess that depends on who's considering her reputation."