Stacie McCarthy pins a badge on the uniform of her husband, Police Officer Denis McCarthy, as their three-year-old daughter Mia Rose McCarthy and Boston Mayor Tom Menino look on. Photo by Bill Forry

Dorchester's Denis McCarthy is a rookie cop, but he's hardly a newbie when it comes to law enforcement or the pressure-cooker of a tough beat.

McCarthy was sworn in - along with 37 other new Boston police officers - last Tuesday in a ceremony at the Washington Irving Middle School in Roslindale. At age 40, he was the second-oldest member of his academy class. His first tour on the streets of South End's district D-4 came on Thanksgiving Day. He missed dinner with the family, but McCarthy was not complaining.

"I can't wait," he said of his first day on the job. "I'd taken the [police exam] so many times, it seemed like it just wasn't in the cards for me."

The Lower Mills native - who has worked for the last 16 years as an officer in the Suffolk County Sheriff's Department, caught a break when the city raised the maximum age for new BPD recruits from 32 to 40 two years ago. But, it was his other career - in the U.S. Marine Corps - that propelled McCarthy into the latest recruit class.

McCarthy has already served two tours in Iraq and could get called back into action as a member of the reserves. His Chicopee-based unit was part of the invasion force that toppled the Saddam Hussein regime in 2003. He rotated back for a second, six-month tour in 2004. McCarthy was based in Fallujah, where his unit helped to protect and assist air missions.

McCarthy is one of 17 veterans in this latest BPD class.

Elaine Driscoll, a spokesperson for the BPD, says that a veteran preference, coupled with raising the age cut-off, has triggered a "welcome change" in the cadet pool.

"Applicants in their mid to late 30s bring tremendous maturity and experience to the job," said Driscoll. "We've seen many who have been working for other law enforcement agencies for years who are now eligible to take the exam, when they could not before because of the age cap. The vets who have been recently activated bring with them a wealth of skills and expertise and training, before even stepping foot in our academy.

Driscoll could not say precisely how many veterans have been added to the ranks in recent years, but said there has been a steady increase since 9/11. Veterans have to take the police officer exam like all other applicants, but they get "prioritized" at the top of the cadet selection list. According to Driscoll, the state offers makeup exams - for anyone deployed when the test is given - every other year.

Captain Timothy Murray, part of the staff at the police academy in Hyde Park, also made note of another statistic in his remarks to the graduating class and their families last week: With this latest injection of new officers, a full 20 percent of the Boston Police patrol force has graduated from the academy since October 2006.

The rigors of the academy came as something of a surprise to McCarthy and his fellow Marine Corps veteran, Michael McHugh, 41, of Brighton. Officer McHugh, who addressed the graduation as class president, served two tours as a special forces member in Iraq and Afghanistan.

"Some of us veterans were joking about it going in," McHugh related. "But [the police academy] turned out to be a great challenge."

McCarthy agreed. "The Police Academy is so much longer than [Marine Corps] boot camp. It's six months and it's pretty demanding. There's a lot in terms of academics."

McCarthy says he went in for extra help on Saturdays and spent at least two hours every night in his studies. His wife, Stacie - with whom he is raising their three-year-old daughter Mia Rose - helped him get over the top.

"If you don't have help at home, you're in trouble," McCarthy said.