Police in Massachusetts reported firing Tasers or stun guns in a record-high 619 cases last year, while threatening to discharge them in about 500 other instances.
That continued a trend in recent years in which the overall use of “electronic control weapons” by police statewide has increased steadily, according to a new report by the state’s Executive Office of Public Safety and Security.
The rising figures are largely driven by a rise in the number of devices issued to officers.
When those figures are factored in, the devices actually have been used at a declining rate.
“The likelihood of an officer using a Taser is down from last year,” said William G. Brooks III, chief of the Norwood Police Department and president of the Massachusetts Chiefs of Police Association.
Brooks said the devices are a valuable tool for police, reducing the potential for injuries to both officers and the people they try to detain.
“One of the big advantages to the Taser is it has a big deterrent effect even if it’s not actually fired,” he said. “Everyone knows what a Taser can do and people want to avoid that so they are less likely to resist.”
If officers do pull the trigger, “if they land on target, it’s very, very effective ... once those Taser probes land on you, there’s nothing you can do.”
But others have raised concerns about the rising prevalence of the devices among officers.
“If a department has Tasers, do they have to use them?” wondered Carl Williams, staff attorney at the American Civil Liberties Union. “Does use just go up because there’s more of them out there?”
“We’d hope that police are using Tasers instead of more lethal options, and if that’s the case, it’s good,” said Williams. “But if they’re used instead of just shouting a command or instead of grabbing someone by the arm and saying ‘Stop doing what you’re doing,’ then we’re in a worse place.”
The problem, he said, is that the state’s data “doesn’t tell us what is really happening.” He also said he was concerned there might be racial bias in the use of the devices.
The state report showed that police in several communities used the devices far more than in most other areas.
Four agencies — New Bedford, Worcester, Lawrence, and Fall River — each reported either firing or threatening to fire electronic control weapons in more than 30 incidents last year. Together they accounted for about one-fifth of all such incidents statewide.
The highest number of incidents was 82 in New Bedford.
More than three-quarters of police departments approved to use the devices reported firing or threatening to fire them in 5 or fewer cases, including 77 agencies that had them but did not fire them at all.
The data covers two kinds of devices that use electricity to stun and temporarily incapacitate people. One type, commonly called a Taser, fires two small, dart-like probes that attach to people. The other type, typically referred to as a stun gun, is brought into direct contact with a person’s skin or clothing.
While designed to be non-lethal tools to subdue potentially dangerous individuals, the devices are dangerous and have killed people.
Amnesty International, which has called for stricter limits on use of the devices, says it tracked at least 675 deaths from electronic control weapon use by law enforcement officials between 2001 and October 2015.
Police in Massachusetts have used the devices since 2004. State public safety officials said they do not track statistics on the number of lethal cases.
But some have made headlines. In May, a 48-year-old man died less than an hour after Fall River police officers tased him. That case remains under investigation by local prosecutors.
In July 2015, a 38-year-old man died after he was shocked with a Taser-like device by Worcester police. The case remains under investigation by local prosecutors.
In June 2014, a 56-year-old man died after Chelsea police tased him. Local prosecutors later ruled that officers “acted reasonably and lawfully” during the encounter.
Brooks said there is always a risk of injury when individuals are physically violent with officers.
“Any time we have someone we’re trying to take into custody and they decide they’re going to take us on, it raises the risk,” he said.
But he said that Tasers and stun guns are less risky than guns. The devices also pose lower risk for injury than alternatives like batons or pepper spray, because individuals are more likely to surrender when threatened with a Taser, he said.
In the vast majority of cases last year, about 90 percent, police issued a warning or multiple warnings — either verbally, with a laser from the device, or by making the device spark, the report said. More than 40 percent of the time, individuals submitted after the warning.
When the devices were fired, individuals were subdued about 77 percent of the time.
The 1,138 times Massachusetts officers either used or threatened to use electronic control weapons during 2015 was an increase of about 10 percent from the year before, and more than double the number from 2011.
A total of 230 law enforcement agencies statewide were approved to use electronic control weapons in 2015, up from 195 in 2014, and up from 123 in 2011. An agency must get the state to sign off on a training program before the agency is allowed to issue the devices to officers.
The number of officers trained to use them rose from about 3,100 in 2011 to 6,500 last year and the number of devices available increased over that same span from 1,650 to over 4,200 a year ago.
Nationwide in 2013, 81 percent of local police departments authorized the use of “conducted energy weapons,” up from 60 percent in 2007 and just 7 percent in 2000, according to the Bureau of Justice Statistics.
But there have been, and still are, some holdouts, among law enforcement.
Brooks said one of the main reasons why more departments don’t use the devices is the cost.
“It’s a very expensive piece of equipment — twice the cost of a firearm,” he said.
Massachusetts State Police began widely arming troopers with Tasers for the first time in March, after the agency spent nearly $1 million to buy 895 of the devices — at more than $1,100 each.
The Boston Police Department still doesn’t arm most officers with the devices. Only members of the department’s tactical teams are equipped with them.
State law prohibits private citizens from possessing electronic control weapons, though that ban has faced legal challenges of late.
Matt Rocheleau can be reached at matthew.rocheleau@globe.com. Follow him on Twitter @mrochele