The story of Rehma Sabir, the 1-year-old Cambridge girl who died in mystifying circumstances three years ago, was always sad and tragic. Now it could get messy and uncomfortable.

Last week, the girl’s parents, Nada Siddiqui and Sameer Sabir, filed a wrongful death lawsuit against their former nanny, Aisling Brady McCarthy, five months after Middlesex County prosecutors dropped murder charges against McCarthy.

The charges against McCarthy were dropped after she spent more than two years in jail awaiting trial for a death that the medical examiner said she couldn’t even classify as a crime.

The official cause of death of Rehma Sabir is undetermined, and the medical examiner, Dr. Katherine Lindstrom, said she wasn’t even sure if the baby had died from inflicted trauma.

In bringing a wrongful death suit against McCarthy, Rehma Sabir’s parents are asserting that their child died at McCarthy’s hands, and are putting forth theories and evidence that were put aside or discredited during a series of pre-trial hearings at which McCarthy’s lawyers, Mindy Thompson and David Meier, were able to peel away the prosecution’s case until there was nothing there.

Rehma Sabir’s parents didn’t sit through those hearings. McCarthy’s sister, Sharon, did and doesn’t believe the parents would have filed suit had they sat and listened to the prosecution’s case unravel gradually until Middlesex District Attorney Marian Ryan was forced to drop the charges.

“Unless you were in that courtroom, and I was, you wouldn’t know,’’ she said. “The parents don’t know any different.’’

Thompson agrees.

“What was unusual about this case is that the evidence, through rulings from the bench, changed drastically and significantly in the courtroom,’’ said Thompson. “The judge asked prosecutors probing questions . . . If the parents were there, they would have questioned the case and the prosecutors. Just listening would have changed their perspective.’’

But they weren’t there. Even if a civil case requires a burden of proof that is less than the criminal standard of beyond a reasonable doubt, the lawsuit against McCarthy seems to go over old, unsubstantiated ground.

Both the parents and their lawyer, Jonathan Friedmann, declined to be interviewed for this column. But they told my Globe colleague, Patricia Wen, that they filed the suit to prevent McCarthy from profiting from Rehma’s death. And Friedmann insisted the parents did go through all the evidence before deciding to file suit.

There has been no suggestion that McCarthy plans to do anything to profit from the child’s death. The parents and their lawyer say they don’t want McCarthy to write a book or make a movie about the case.

McCarthy, who had been living in the United States illegally, was deported to her native Ireland after the murder charges were dropped. When I interviewed her there last month, McCarthy said she wanted to sue Dr. Alice Newton, who made the initial diagnosis that led to her arrest, and Middlesex County prosecutors, not to get money, but to expose a system that allows people to be accused of murder on evidence that doesn’t stand up to scientific scrutiny.

Thompson scoffed at the idea that McCarthy is looking for money.

“She has no intention of profiting from the death of a child,’’ she said. “What she wants is the Middlesex DA’s office and Alice Newton to stop doing this to people. To the extent that Aisling is talking about this, it’s to help educate people and make sure that no one goes through the living hell she went through. She’s never spoken badly of the parents.’’

And there’s the rub. The wrongful death suit against McCarthy puts her and her lawyers in the awkward position of pointing out that the parents, or people they visited when they took their daughter abroad against a doctor’s advice, were just as likely to have caused injuries to Rehma as McCarthy was. And the madness of being put in that position is that the medical examiner’s findings don’t support either of those conclusions.

Beyond asserting her innocence, McCarthy and her lawyers say investigators rushed to judgment, concluding that she was responsible for the child’s death without seriously considering other explanations.

If the criminal charges against McCarthy had not been dropped and the case had gone to trial, McCarthy’s lawyers say they would have been duty-bound to put into evidence some things that could be uncomfortable for the parents, including postings to an on-line mother’s advice forum by someone using Siddiqui’s name and e-mail address.

If this lawsuit goes forward, Thompson said, “Yes, those would come out.’’

The prosecution alleged that McCarthy lost her patience with the crying child and inflicted traumatic injuries. But McCarthy had been a nanny for 10 years, and there was no evidence that she ever lost her patience with a crying child.

Thompson noted that police never interviewed Rehma Sabir’s parents separately, which is common practice in such a case, where all of a child’s caregivers would be considered either suspects or crucial witnesses. Instead, the police zeroed in on McCarthy, especially after Newton quickly concluded that only McCarthy could have inflicted the injuries that killed the baby.

But, of course, the medical examiner said it’s not clear what killed the baby, and that it could just as easily have been an undiagnosed illness.

Maybe something will be worked out. Maybe this will all go away. If it doesn’t, it could get ugly.

Kevin Cullen is a Globe columnist. He can be reached at cullen@globe.com.