Ellen Greenberg died in the kitchen of her Philadelphia apartment on the afternoon of a snowstorm in January 2011.

Schools had let out early on account of the weather, and the 27-year-old first-grade teacher had headed home to the two-bedroom unit she shared with her fiance, Sam Goldberg. Hours later, after he returned from the gym, he found Greenberg dead. A knife had been plunged into her chest, one of 20 stab wounds discovered on her head, neck and torso.

For five weeks, investigators waffled on what happened. Upon first review, there were no suspects — Greenberg, police said, was alone inside the apartment, which had been locked with the interior swing bar. Neighbors did not report hearing a disturbance, and there was no security footage or stolen property to suggest an intruder. What’s more, Greenberg appeared to have no defensive wounds, and no DNA but hers was found on the knife and her clothing.

The death was initially worked as a suicide, then — after an examination by the medical examiner’s office — as a homicide. But after further investigation, the final determination in March 2011 was that Greenberg had taken her own life.

For Greenberg’s parents, that conclusion never sat right. In a lawsuit against the medical examiner’s office, the Greenbergs have challenged that finding and accused officials of a sloppy investigation. Earlier this month — two years after filing the case and gathering evidence — their legal team argued in front of a Philadelphia judge that the autopsy ruling should be overturned.

“It makes no sense,” the Greenbergs’ attorney, Joseph Podraza, told The Washington Post.

He said Greenberg’s parents are motivated by one driving force: love.

“They want to know what happened to their daughter,” he said.

Last week, the judge issued an order paving the way for the case to head to a civil trial, although no dates have been set at this time.

“We look forward to the trial in the hopes of obtaining justice for Ellen,” Sandra Greenberg, Ellen’s mother, told KYW-TV.

A city attorney representing the Philadelphia Medical Examiner’s Office and medical examiner Marlon Osbourne, the defendants in the case, did not respond to an interview request from The Post. But in court filings, the city’s lawyer, Ellen Berkowitz, has contended the Greenbergs have no legal claim to overturn the manner of death.

“They essentially ask this Court to sit as a sur-medical examiner, to overrule the determination of the medical professional vested by state law and the Philadelphia Code with the sole responsibility and discretion to determine the cause and manner of death,” Berkowitz wrote in an August court filing.

Ellen Greenberg died on Jan. 26, 2011. That morning, she spoke with her mother around 7 a.m. as they both were headed to work. Because of the snowstorm, school got out early that day; Greenberg stopped for gas around 1:30 p.m. before returning to her apartment.

Her fiance would later tell police that he went to the building’s gym around 4:45 that afternoon. When he returned about 45 minutes later, he said, the apartment was locked from inside with the swing bar. According to a medical examiner’s report reviewed by The Post, he shouted to Greenberg and texted her nine times, becoming increasingly irritated.

“Hello”

“open the door”

“you better have an excuse”

Finally, he said, accompanied by the building’s security guard, he forced his way into the apartment, breaking the lock. Greenberg was dead in the kitchen. He called 911 around 6:30 p.m.

Police found no evidence of an intruder. The six-story apartment could be accessed only from the front door and an exterior balcony, but the fresh layer of snow outside was undisturbed. Officers noted there was nothing to suggest a robbery; plenty of valuables were visible around the home. Greenberg’s parents told police they had no reason to suspect her fiance, and Greenberg’s psychiatrist, whom she had been seeing for anxiety, reported that Greenberg was happy in the relationship and had denied any abuse.

With no suggestion that another person had been inside the apartment, police at the scene suspected the death was a suicide, noting in particular the lack of defensive wounds on Greenberg’s body.

But the next day, Osbourne reached a different conclusion. In a Jan. 27 report, the medical examiner classified the death as a homicide.

Nevertheless, the investigation continued. After learning about Greenberg’s anxiety, police told the Philadelphia Inquirer they were “leaning” toward a determination of suicide. Her psychiatrist had prescribed her Klonopin for anxiety and Ambien, a sleep aid, both of which list suicidal ideations as possible side effects, although no one close to Greenberg had heard her express any thoughts of harming herself.

Armed with more information, Osbourne on March 3 changed the death certificate to reflect that Greenberg’s death was a suicide, according to the lawsuit.

Greenberg’s parents were in disbelief. “I was in so much shock,” Sandra Greenberg told the Inquirer.

Questioning the determination, Greenberg’s parents requested the investigative reports, retained lawyers and hired experts. Those experts pointed out several reasons Greenberg’s death may well have been a homicide. If Greenberg had planned on killing herself, they asked, why had she filled up her gas tank after leaving school? Why had she not left a note? Why was a half-finished fruit salad found on the kitchen counter above her body? If she was intent on taking her life, why had she chosen to stab herself, and why had she done so through her clothing, something one expert noted is rare in cases of suicide by stabbing?

In the ongoing lawsuit against Osbourne and the Philadelphia Medical Examiner’s Office, Podraza, the family’s attorney, has argued there are reasons to suggest the death was or could have been a homicide. The knife block in Greenberg’s kitchen, for instance, was overturned on its side, potentially indicating a struggle. A dried blood drip on her face suggested her body may have been moved. And a large gash at the back of Greenberg’s head may have incapacitated her, possibly explaining why she was unable to defend herself.

Podraza also obtained surveillance footage and a statement from the apartment’s security guard confirming he was not with Greenberg’s fiance when he breached the door that night. (Goldberg did not respond to a voice mail or text message from The Post asking to discuss the case.)

In sum, Podraza believes it’s all enough to warrant changing the manner of death to homicide or, at the very least, classifying it as undetermined.

“We now know, as far as I’m concerned, that this was not a suicide,” he told The Post.

The attorney for the city of Philadelphia, meanwhile, argues that Osbourne and the medical examiner’s office made an informed determination based on years of professional experience. In court filings, the city argues that the Greenbergs’ legal team has misinterpreted statements by personnel in the medical examiner’s office to fit a narrative suggesting homicide. And it says another apartment worker may have accompanied Greenberg’s fiance when he broke down the door if the guard did not.

Further, the city says police could still investigate Greenberg’s death as a homicide if it wanted to, even while the death certificate says suicide.

“The medical examiner’s determination is binding on no one. … If a prosecuting authority were convinced that Ellen Greenberg was murdered, there is no statute of limitations on homicide and they could pursue it,” reads an August response from the city.

Podraza said Greenberg’s parents hope someday for a “forthright, complete investigation.” But for now, they’re simply after the answer to a difficult question.

“Is this a suicide, or is this something else?”