PHILADELPHIA (CBS) --their fight to have her death listed as a homicide -- even though a Pennsylvania appellate court ruled against them last week.
-- and lawyers for the Greenbergs allege the investigation was mishandled.
Sandra and Joshua Greenberg were dealt another legal setback in unlocking the mystery surrounding their daughter's 2011 death.
"We don't believe our daughter committed suicide," Joshua Greenberg said.
The Philly teacher was found dead with 20 stab wounds and "died by suicide," according to the medical examiner. But that same medical examiner initially listed the manner of death to be homicide before changing it to suicide.
That reversal and other steps taken in the 2011 case have cast doubts about the investigation, according to the Greenberg's attorneys, their experts who have reviewed the case and the Greenbergs themselves.
Joe Holden: "What happened?"
Joshua Greenberg: "With the stroke of a pen, we could be finding out what really happened to our daughter. We could find out what's called the truth."
The Greenbergs, speaking with CBS News Philadelphia in their Harrisburg-area home, have been fighting to reverse the suicide ruling on their daughter's death certificate.
The Commonwealth Court, in a 2-to-1 ruling, found the Greenbergs lacked standing to bring their claim, meaning simply that they can't raise this challenge.
The court also indicated it "had no choice" but to rule against the Greenbergs in their quest to change the death certificate due to procedural restrictions.
But in its opinion, the court did raise questions about the authorities who first investigated Ellen's death.
"They [judges] have blatantly said the investigation was faulty on the part of the police, on the part of the medical examiner, on the part of the district attorney," Joshua Greenberg said.
Attorney Joe Podraza represents the Greenbergs and was stunned by the court's ruling. He said it seemed to side with his clients, but then rules against them.
"Three judges say there is a completely flawed investigation, and it goes across three parts of our government -- the medical examiner's office, the district attorney's office and the Philadelphia Police Department," Podraza said.
Holden: How does that happen?
Podraza: "You tell me, Joe."
in January 2011.
Ellen Greenberg's fiancé was at the gym -- returning to find their Manayunk apartment door deadbolted, according to court records.
After an hour of trying to reach her, records show he broke down the door to find Ellen slumped in the kitchen.
Medical examiner's records show Ellen had been stabbed in the head, neck and chest.
One neck wound was found without any trace of blood, according to a review of Ellen Greenberg's autopsy records.
"There is no blood there, meaning she was dead at the time that wound was administered," Podraza said. "Even the city's person said I would believe this is a post-mortem or after she was dead stab wound."
Holden: "That's murder."
Podraza: "And that's not even the last wound we know for sure because the knife was found in her chest."
"To say this is a suicide is to say that Ellen stabbed herself twice after she was already dead. Doesn't even make any sense," Podraza said.
Sandra Greenberg says she had a pleasant phone call with her daughter the morning of her death.
Records show Ellen was being treated for an onset of anxiety, but Greenberg's experts said it's unlikely the medications factored into suicidal thoughts and there was no suicide note.
"Our daughter was brutally attacked, brutally murdered," Sandra Greenberg said. "One stab wound, two stab wounds. That sounds more like rage."
The Greenbergs have also filed suit against the city to force the release of surveillance video from apartment hallways collected by the police as well for the police case file.
They're also suing the medical examiners alleging they covered up a homicide.
"There are clearly reasons why agencies don't want us to get deeper into this case," Podraza said. "This is clearly a murder and should be investigated as such," Podraza said.
Holden: "Do you think someone is obstructing this investigation?"
Podraza: There's something going on here plainly interfering with it. I don't know what it is."
The City of Philadelphia provided a statement, saying they were pleased the court agreed with them, adding:
"If Mr. and Mrs. Greenberg have new evidence about their daughter's death, we urge them to present it to the investigators in Chester County, as they have the authority to reopen the investigation in this case."
due to conflicts of interest in the Philadelphia District Attorney's Office as well as the State Attorney General's Office.
The Greenbergs admit lying awake at night trying to reconstruct their own daughter's death investigation. Meanwhile, it's hard to think about the time lost without their daughter, Ellen.
"I try not to dwell on that even though there is a big hole in my heart," Sandra Greenberg said.
Even though it ruled against the Greenbergs, the Commonwealth Court went over the facts of the case in detail saying it did so "with hopes that equity may one day prevail for the victim and her loved ones."
This court opinion wasn't unanimous.
A third judge sided with the Greenbergs – believing they had standing to sue to reverse the death certificate from suicide back to homicide.
The Greenbergs are intent on taking this to the Pennsylvania Supreme Court.
It's unknown if the court would take up the matter.
for more features.