Fatal stabbings exceeded gun deaths in NYC in November. Experts say that's rare.

Twice as many people were killed in stabbings in New York City than shootings last month, police data shows — a pattern that experts said may be fueled in part by a spike in mental health crises among alleged assailants.

Six of the stabbing victims, or more than a third, were killed in their own homes, according to police information, and experts said knives show up more frequently in domestic than street violence. But authorities have not confirmed exactly how many of the overall incidents they believe involved suspects in crisis.

“[It] may suggest an increase in homicides by those suffering from mental illness, and that would represent a break with historic patterns in the city,” said Fritz Umbach, a criminology expert and professor at CUNY’s John Jay College of Criminal Justice.

The number of gun homicides in the city started to surpass knife killings after crack cocaine arrived in the mid-1980s, he said, and that trend has largely kept up since then. But in November, 16 people were killed in stabbings, compared to eight in shootings. Umbach said a continued citywide decline in gun violence could also play a role in the disparity.

Nearly 350 people were killed in the city through Dec. 1 this year, a 6% decrease from the same period last year, according to NYPD data, which does not break down the number of shooting and stabbing deaths. Gothamist’s analysis of individual homicide reports, though, shows 177 people were shot to death citywide this year, not including the 12 people who have been shot and killed by police.

There is scant research on the convergence between mental health and stabbings in New York City, but people with mental illnesses are about five times more likely to use a knife than a gun to carry out an attack, according to a 2004 national study of 270 murder defendants who were court-ordered to undergo competency assessments. The study also found that defendants with severe mental illness and a substance use disorder were 13 times more likely to use a knife than other weapons.

In the city, the most recent high-profile example was the unprovoked stabbing spree on Nov. 18 that left three people dead across Manhattan. Police said 51-year-old Ramon Rivera, a homeless man with a complex history of mental health issues, killed two men and a woman at different locations within just a few hours that morning. Rivera was arrested and charged with murder in all three killings. His attorney, who did not immediately return a request for comment, asked for a competency evaluation for Rivera before entering a plea and records show he is due in court later this month.

Police said they made arrests in six of the other 13 November cases. Neither court documents nor police reports have yet made clear whether mental health played a part in any of them. Attorneys for the defendants in those cases did not answer calls seeking comment.

But Darryl Delyons, who lost his 66-year-old mother and 91-year-old grandfather in a fatal double stabbing on Nov. 10 at the family's Cypress Hills home, said he suspected some kind of mental break was a factor in their deaths.

Police arrested and charged 46-year-old Kerry Lewis the next day with both killings. Delyons said Lewis was his mother’s longtime live-in boyfriend and had no record of domestic violence or any other concerning behavior. Police confirmed Lewis had no prior arrests or domestic incidents on file, and his lawyer did not respond to a request for comment.

“I've never heard Kerry curse a day in my life. I've never seen him touch my mother ever in 24 years of them dealing with each other,” Delyons said in an interview last week. “No one could understand what would drive him to do something this hideous. It just doesn't add up.”

Delyons added that there were no signs that something was off with Lewis or his family members on the day of the incident.

“Everything was harmonious,” Delyons recalled. “My mother had been preparing dinner, my grandfather had been in his room watching the football game.” He recalled that he was on his computer working on a project at the time and then left the house on Warwick Street to meet his aunt in Downtown Brooklyn.

Hours later, Delyons said he got the call from a family member that his mother, Jacqueline Delyons, and his grandfather, Roosevelt Simmons, had been killed.

Random knife attacks, like the string of stabbings allegedly carried out by Rivera, are rare. But Umbach said they can be even harder to prevent than shootings, because knives are easier than firearms to get and hide.

“Knife homicides are very resistant to traditional police methods,” he said. “While a stop-question-frisk can often find a gun … it's much more difficult to find a knife through a stop-question-frisk. It's less visible to the officer and not always discoverable in the pat down that's allowed.”

The NYPD reported three fatal stabbings in three separate incidents in the first week of December, and the victims were an 87-year-old woman, a 38-year-old woman and a 17-year-old boy in three separate incidents, according to police. The 87-year-old, identified as Laxmiben Khristi, was killed in her home, officials said. A fourth stabbing was reported earlier this week that left a 26-year-old man dead.

Delyons said he's hoping for some kind of explanation as to why Lewis allegedly perpetuated such a vicious attack on his mother and grandfather, leaving them both lying in the kitchen with their throats slit, according to the criminal complaint. He said detectives haven’t had much new information to share with him about their investigation, adding that he was struggling to process the tragedy as he planned funerals for the “two core members” of his life.

“When [my daughter] was a baby, she used to sleep between him and my mom,” he said. “Nobody saw this coming.”