As the mounting number of DNA exonerations reveals, America’s criminal-justice system is ill-equipped to deal with the rapid pace of scientific advances. A new group of criminal convictions based on what was once considered incontrovertible medical evidence is now under scrutiny—prosecutions based on shaken-baby syndrome (SBS).

Unlike most crimes, injuries and deaths assumed to be from SBS have no adult witnesses other than the accused. They take place in intimate settings, usually when a caretaker and an infant are alone together. According to a New York Times article, law enforcement officials estimate that in 50 to 75 percent of these cases, there is no other evidence of child abuse: no bruises, broken bones, or burns. These cases are usually portrayed like this: Someone snapped. An otherwise gentle person, often a caregiver with years of experience, loses it and shakes or bashes a baby’s head against the floor or wall. At trial, a prosecutor may hold up a doll and show how forceful the motion would have been to cause such injuries. It’s a crime behind closed doors. As a result, proving innocence in these cases is often in the hands of medical experts.

This May, Jennifer Del Prete was released from prison after a federal judge in Illinois found that the scientific evidence of SBS that prosecutors used to argue that Del Prete had shaken a 4-month-old infant to death was “unscientific and thus unsupportable.” She had already served 10 years of a 20-year sentence. The judge went on in his opinion to point out, “the mechanism by which shaking purportedly causes these sorts of injuries is as yet unclear, assuming it exists at all.”

A diagnosis of SBS relies on a series of three symptoms called the “triad”: brain bleeding, retinal bleeding, and brain swelling. Physicians assumed that shaken babies would show immediate evidence of brain injury. As a result, even without any other evidence of abuse, the last known caretaker became the primary suspect when a baby who died was found upon examination to have the triad. The diagnosis became increasing common in criminal trials throughout the 1990s and 2000s, when SBS cases became routine. For many lawyers, the triad was considered a reliable standard for such prosecutions, which Deborah Tuerkheimer, a law professor and former Manhattan assistant district attorney, describes in her book Flawed Convictions: “Shaken Baby Syndrome” and the Inertia of Injustice.

As medicine advanced, however, more doctors began to question whether SBS can be a definitive diagnosis—and whether some of those who are in prison are actually innocent. In recent years, medical experts have hotly debated the classic triad of SBS, suggesting that these symptoms may also sometimes occur as a result of other injuries, such as a relatively short fall. In 2011, a Canadian pathologist published a report disputing the traditional understanding of SBS. Dr. Norman Guthkelch, a now-retired doctor widely credited for first discovering SBS, told NPR that he intended for his research to assist in education and prevention; he isn’t convinced that the triad of symptoms can be used to definitively argue that someone has shaken or battered an infant. The American Academic of Pediatrics website now substitutes “Abusive Head Trauma” for SBS, “in recognition of the need for broad medical terminology that includes all mechanisms of injury.” The suggestion is that SBS is not longer viable as a definitive diagnosis.

But not everyone agrees that SBS convictions should be re-examined. The National Center on Shaken-Baby Syndrome, a nonprofit dedicated to preventing child abuse, argued in an official response to the ongoing debate, “While very rare, wrongful convictions do occasionally happen, but by no means is shaken baby syndrome/abusive head trauma a ‘flawed diagnosis’ being used to convict innocent individuals of child abuse.”

Tuerkheimer pointed out that the Del Prete decision is notable because the facts of her case were so typical. Del Prete was a childcare worker for a small home daycare in a suburb of Chicago. She told authorities that when she picked up the 4-month-old Isabella to feed her, she was limp. Del Prete called 911 and commenced CPR. There were no witnesses and no other signs of abuse, such as bruising or broken bones. Del Prete also has two other children of her own. Her conviction was solely based on the presence of the triad of symptoms; there was no other evidence against her, and she consistently denied that she had injured the baby in any way.

While Del Prete has finally found justice, there are potentially hundreds of other similar prosecutions yet to be reexamined. The Wisconsin Innocence Project told the press that at least 19 cases relying solely on SBS have been overturned in recent years. Professor Carrie Sperling, co-director of the Wisconsin Innocence Project, said that this is likely a low estimate because these cases can be difficult to track. Sperling and her team are currently representing Jennifer Hancock—a woman convicted in 2009 for causing the death of 4-month-old Lincoln Wilber—in an appeal to overturn her conviction, another case based on textbook SBS. In Hancock’s case, the key witness, a forensic pathologist named Dr. Michael Stier, has significantly altered his testimony. Where once he testified that the victim’s injuries could only be from abuse, he is now less certain. Sperling confirmed that Stier recently said that bleeding in the brain, once considered a hallmark of SBS, could no longer be used as the sole indicia of abuse.

Yet, prosecutors still try SBS cases and win. Tuerkheimer argues that the criminal justice system has not moved quickly enough to account for the changes in scientific evidence. She pointed out that in many cases, the infant victims were also suffering from other physical conditions, which may have contributed to their injuries. But, because experts and judges considered the triad of SBS conditions definitive, many defendants were unable to contradict the evidence against them. Some may have given wrongful confessions because the investigators led the defendants to believe that the scientific evidence was absolute.

In the case of Keny Medrano-Cambara, who refused to admit to harming 16-month-old Brianna after hours of police interrogation, the judge determined that the scientific evidence was too shaky for conviction. Mendrano-Cambara had already spent 16 months in jail and, after her acquittal, authorities began the process to deport her.

Like Medrano-Cambara, Del Prete, and Hancock, many of the most well-known cases involving SBS are women caring for other people’s children. The Medill Justice Project, based at Northwestern’s School of Journalism, has identified more than 3,000, cases since SBS was first identified in 1971, involving prosecutions based on shaken-baby syndrome. For years, the director Alec Klein told me, journalists have avoided this topic because it relies on complicated and often contradictory medical and scientific evidence. Klein said, “When I asked my students for background, we found none.” This became the impetus behind the database. He wanted to create a statistical resource that could be used to give some context to these legal proceedings.

One surprising finding of the database shows that an overwhelming number—72.5 percent—of SBS accusations are made against men. The statistical evidence goes on to indicate that certain counties are “hot spots” for SBS prosecutions, among them San Diego County, Harris County (which includes Houston, Texas), and Cook County (which includes Chicago, Illinois). As Klein points out, the evidence itself cannot be linked to any dispositive cause. It does, however, provide some background for those hoping to improve educational and outreach efforts.

Tuerkheimer suggested that one reason why SBS prosecutions continue to be unexamined is because they legitimize social fears about mothers who leave their children in the care of others. “We have extreme cultural anxiety around working mothers,” she said. She also pointed out that many of these cases involve class issues, and that many of these caretakers “are not the fortunate or the privileged.” Medrano-Cambara, for example, did not speak English very well. Del Prete recalled that before her arrest in 2002, she had just recently gotten back on her feet financially.

Del Prete was finally released on April 30, 2014 and reunited with her children. “This hurt everyone involved, not just me,” she said in a press statement.

The results of wrong convictions and accusations can be devastating, resulting in separation from children and the loss of a stable life. Mendrano-Cabrera eventually returned to her home country of Guatemala rather than battle immigration claims. She and her husband are suing county officials and the experts who testified against her for what her husband has told reporters was “irretrievable harm.”

While new medical evidence and better advances in diagnosis may curtail future prosecutions based solely on the classic SBS triad, the justice system has been slow to change. There has been no systemic response to determine whether there are more cases of actual innocence, like Del Prete’s. Tuerkheimer said that our justice system is “primed to value finality in ways that are not reflective of other concerns, like accuracy.”