A man convicted of bludgeoning four homeless men to death was sentenced to 40 years to life in prison on Thursday, in a case that a Manhattan judge said highlighted the city’s challenges addressing mental health, homelessness and violence.

In February, a jury took less than a day to find that the man, Randy Rodriguez Santos, had intentionally killed the victims, whom he attacked as they slept in Manhattan’s Chinatown in October 2019. The jury rejected the argument from Mr. Santos’s lawyers that he should be found not guilty because of mental disease or defect.

The judge who sentenced Mr. Santos, Laura A. Ward of State Supreme Court in Manhattan, said that Mr. Santos’s case exemplified the “coming together of three horrible symptoms of this city: homelessness, mental illness and narcotics abuse.”

“I’ve been on the bench for about 30 years, and those are the three things that seem to be the constant in almost all of our violent crime cases,” Justice Ward said.

The men who were killed, whose ages ranged from their late 30s to their 80s, were Anthony L. Manson, Nazario A. Vazquez Villegas, Chuen Kwok and Florencio Moran Camano.

The news of the killings highlighted the vulnerability of people living on the street in New York and demonstrated how people with severe mental illness, even those who are known to city agencies, can fall through the cracks. In the years since, episode after episode of violence, some of it fatal, has reignited concerns over the safety of homeless New Yorkers.