The decision to vacate Jones' conviction was issued Monday. Krasner said he is confident an appellate court will reverse the ruling and allow the conviction to stand.
If not, though, Krasner says his office is prepared to pursue a new trial.
"We will be re-trying it vigorously because, as I said, we believe this conviction is factually, morally, legally correct," Krasner said.
The judge's decision appears to be based on the involvement of former Philadelphia police detective Philip Nordo in the case.
Nordo was later convicted of sexually assaulting suspects and witnesses.
Krasner said Nordo's involvement in the investigation had no impact on Jones' trial or conviction. That view is shared by Walker's mother, Wayniya Walker.
"Circumstances have once again brought our family before cameras, microphones, requiring us to revisit the darkest chapter of our lives," she said.
Walker was off duty when he was killed near a bus stop in 2012.
The ruling is not expected to affect Jones' co-defendant, Chancier MacFarland. MacFarland pleaded guilty to his role in the case, testified against Jones and is serving a prison sentence of 20 to 40 years.
Roosevelt Poplar, president of Fraternal Order of Police Lodge 5, said the union continues to support Walker's family.
"This is a tragedy that can never be forgotten. So, we are always there for her. She knows that, and that's our main concern, to make sure she is aware that the FOP will be there for her and her family," Poplar said.
There is no indication that a bail motion will be filed in the case, and Jones is expected to remain incarcerated as the legal process continues.
Prosecutors identified Jones as the gunman, and he was sentenced to life in prison following his conviction.