Police Commissioner Raymond Kelly turned this week’s anniversary of the arrest of the “Son of Sam” serial killer in 1977 into a warning about the city’s police recruiting crisis.

Noting a dip in police recruitment numbers this year, Mr. Kelly reminded New Yorkers at a conference at John Jay College of Criminal Justice commemorating the serial killer’s eventual capture that it came two years after layoffs crippled the police force.

“I think there are lessons to be learned there,” Mr. Kelly said. “The layoffs were profoundly debilitating to the department.”

Mr. Kelly was referring to the 5,000 police officers laid off during the city’s 1975 financial crisis, which he argued directly contributed to the initial difficulty detectives had in finding the killer, David Berkowitz.

“It always seemed like we didn’t have enough cops to do anything,” Mr. Kelly, who was working as a lieutenant in Midtown Manhattan at the time, said. “There was this feeling of despair and lethargy in the department.”

Mr. Kelly has blamed a drop-off in the number of police recruits signing up this summer to the $25,100 beginning salary under the current union contract.

This time, Mr. Kelly said, the situation isn’t as bad. “It was a much different mood in 1975,” he said. “I think we’ll get over it.”