In addition, some counterterrorism experts said efforts to define domestic terrorism risked becoming purely symbolic.
Mary McCord, a former top national security official in the Justice Department, said states’ existing domestic terrorism laws have not proven very effective, in part because they do little to address crime prevention.
“They kind of just sit there unused, because they don’t necessarily have the same experience in investigating and prosecuting terrorism cases” as federal authorities, she said. “I think all states should have domestic terrorism statutes, it’s a good thing for them to have, but it hasn’t really moved the ball significantly.”
Brian Michael Jenkins, a senior researcher at the RAND Corporation, said that murder, whatever the motivation, typically already carries the maximum penalties.
“A mass murderer with a manifesto is still a mass murderer,” Mr. Jenkins said.
“Prosecutors, if they have something like a murder — that’s a good case to go on, and they are not necessarily interested in complicating the case by getting into a discussion of political motivation,” he added.
Indeed, it is unclear just how much effect the proposal would have. Current hate crime law covers only second-degree, not first-degree, murder, and those convicted can qualify for parole; the governor’s proposal would close that loophole, according to Mr. Cuomo’s office.
But Ms. McCord said New York law also already provides for murder in aid of terrorism, under the state’s broader definition of terrorism as an attempt to intimidate civilians.