Spike in crime often accompanies Fourth of July

David L. Ryan/Globe Staff/File

At Boston Medical Center’s trauma center, few things are predictable, but one of them is that there will be a flurry of activity on the Fourth of July.

For the past several years, the holiday has ranked as the busiest day of the year for treating shooting and stabbing victims, according to Thea James, the hospital’s Violence Intervention Advocacy Program director. July 5 has been the second busiest.

The Fourth may evoke pleasant images of parties and sun-splashed cookouts, but it’s also a day that violence spikes in some major cities. Large gatherings and sometimes alcohol-influenced decisionmaking drive up the number of shootings, stabbings, and other violent crimes, police say.

According to a Globe analysis of Boston police logs from 2008 to 2014, July 4 had significantly more violent crime — assault and battery, sex assaults, robberies, and murders — than the typical day. The department received a median of 54 calls reporting violent crime on July 4, compared with the overall median of 37.

Boston police have also noticed higher numbers of domestic violence calls on July 4, said police spokesman Lieutenant Detective Michael McCarthy. The median number of domestic violence incidents occurring on a given day from 2008 to 2014 was 29, according to the Boston police logs, but on July 4, it soared to 41.

Sometimes Independence Day has proven deadly. In 2011, for example, four men were killed in the city in a span of five hours.

The spike in violence is not a problem unique to Boston. Last year, 82 people were shot — 16 fatally — over the Fourth of July weekend in Chicago. Seven people suffered gunshot wounds in Indianapolis that weekend. Six were hurt by gunfire at a music festival in Houston.

“I’m aware this weekend is always a troubling weekend,” Police Commissioner William B. Evans said Friday at a news conference on safety preparations for the weekend. “Any city you look at, July Fourth tends to be a violent one. We’re working hard to make sure this is a great weekend and a safe weekend.”

In Boston, the rise in crime during the summer months, and particularly on the Fourth holiday, is a matter of volume, McCarthy said. When more people are outside on the streets, there’s more opportunity for crime.

“With July 4th being the kickoff for summer, that’s when we tend to see incidents occur,” said McCarthy. “Groups of people get together, kids are out of school, and people are on vacation. More people are out to be both victims and perpetrators.”

Alcohol also “tends to be present at large gatherings and that can increase tension and lapses in judgment,” he said.

The day may also be an emotional time for some who have suffered losses on past Fourths, said James, the Boston Medical Center official.

“It triggers young people. They begin to think about their friends who have lost their lives on this holiday,” she said, noting that that can sometimes lead to revenge attacks.

While the Boston police plan to support State Police at the festivities at the Esplanade, their primary focus this Fourth will be patrolling the city’s neighborhoods, said McCarthy. Forty new officers will be sent to the city’s most crime-ridden areas, as well as increased numbers of community, bicycle, and gang task force officers.

Police have increased their presence on July 4 in past years, but this year’s holiday poses even more of a challenge, McCarthy said.

“It’s tough when July 4th falls on a Saturday,” he said, which means even more people are likely to have time off work. “More outside activity yields itself to an increase in activities that we need to respond to.”