New York City’s social safety net has repeatedly failed to prevent mentally ill people from unraveling on the streets and committing random acts of violence.

It is a problem that generations of city leaders have tried and failed to solve. It became a priority for Mayor Eric Adams two weeks after he took office, when a homeless mentally ill man named Martial Simon pushed Michelle Go, a 40-year-old financial consultant, in front of a subway train in Times Square, killing her.

Before the fatal subway shoving in January 2022, Mr. Simon, then 61, had been hospitalized at a state psychiatric facility and released despite signs that he was still delusional — the kind of institutional breakdown that has preceded scores of other attacks, a New York Times investigation has found.

Times reporters spent more than a year examining how often homeless mentally ill people under the care of the city have committed acts of violence, conducting more than 250 interviews, obtaining tens of thousands of pages of confidential treatment records and visiting courthouses, jails, prisons and a psychiatric ward. The examination identified 94 instances in the past decade in which breakdowns of the city’s social safety net preceded the violence, sometimes by days or hours.

Here are five takeaways from the Times investigation.

The major elements of the safety net were stitched together after the state began closing its notorious psychiatric institutions in the 1960s. They consist of homeless shelters that are supposed to connect people with services and support, private and public hospitals that are tasked with stabilizing them during crises and specialized treatment teams that are designed to function as mobile mental health clinics.

But the Times examination found a widespread failure by the agencies to share information, even though New York State created a detailed database years ago for that purpose. It also revealed a pattern among the agencies of taking the narrowest possible approach to care, and an unwillingness on the part of city and state officials to fully fund crucial programs, leading to understaffing and harried treatment.

New York City’s sprawling shelter system relies on some 600 sites operated by nonprofit contractors across the city. It includes 37 dedicated mental health shelters that are staffed with psychiatrists and social workers to offer treatment — at a cost to taxpayers of about $250 million a year.

But the city has failed to reliably place mentally ill people in them thanks to flaws in the shelter system’s intake process. The system relies on low-paid workers who lack the mental health training and tools to identify psychiatric issues in newcomers. Often, the workers must rely on people to self report mental illness. As a result, many of the initial assessments that decide shelter placements have been incorrect. One in four people with severe mental illness in the shelter system were not placed in a mental health shelter, state auditors found in 2022.

The results can be disastrous. One 41-year-old man who should have been placed in a mental health shelter was instead shuttled to other types of shelters as his mental health deteriorated. In August 2021, he used a hammer to attack a stranger on a subway platform in Union Square, badly injuring him.

New York’s private hospitals run the vast majority of emergency rooms in the city, but they have cut psychiatric inpatient beds to boost their bottom line and resisted admitting patients who rely on Medicaid rather than private insurance, records and interviews show.

As private hospitals have moved away from caring for homeless mentally ill people, they have placed a disproportionate burden on the city’s public hospital system, NYC Health + Hospitals. Those hospitals have repeatedly erred in their treatment of homeless mentally ill people while being overwhelmed by nearly 50,000 psychiatric patients per year.

One patient, a 29-year-old mother, had a history of schizoaffective disorder and violent outbursts when she was brought to Harlem Hospital Center in January 2021. The emergency room doctor sedated her “due to concern for safety of patient and staff,” records show, but did not seek to admit her for inpatient care. Instead, she was discharged. Still unstable two weeks later, the woman pushed another woman onto the tracks of a Bronx subway station, injuring her.

A network of special treatment teams, run on a contract basis, was supposed to be New York’s solution for caring for high-risk, mentally ill people on the streets. But the state has starved the teams of funding, leading providers to pay caseworkers low wages and saddle them with staggering caseloads. Some teams spent just 15 minutes per visit with patients — the minimum amount of time required to bill Medicaid for services.

One man under the care of a specialized team became increasingly violent as his team stood by, doing little to intervene. Eventually, the man, 23, shoved a stranger onto the tracks at the subway station in Bryant Park, injuring him.

One reason city and state agencies have repeated the same errors again and again traces to medical privacy laws that protect patient confidentiality but keep mistakes hidden from public view.

The lack of public information about the failures of shelters, hospitals, specialized teams and other organizations makes it difficult to evaluate the breakdowns that precede acts of violence or hold officials accountable for them.

The agencies that run the city’s homeless shelters, hospitals and mental health programs refused to answer questions about failures in specific cases, citing patient privacy laws. They declined to discuss the failures even when provided with signed privacy waivers giving them permission to do so.

“The public has been gaslit for nearly four decades,” said Mary Brosnahan, who spent 30 years leading the Coalition for the Homeless, a New York advocacy and service organization. “We keep being told something is done, but nothing has changed. There is constant finger-pointing at every level of government and dropping the ball with the hopes that it won’t result in another Michelle Go.”