"This is a young person's job," Watertown Police Chief Joseph J. Goss said, "but there is no trade-off for experience, in any profession."

Jefferson County Sheriff John P, Burns agreed: "You can't replace experience."

Both department heads are dealing with that transition.

When several Watertown police veterans retired in the summer, opening the door to young blood, the department's membership age average dropped to about 37, the lowest since 1999, when the average was 36.5.

But more revealing, Chief Goss said, is, "We have 30 officers with less than five years on the job, and that is double what it was in 1999."

The average age at the sheriff's office is also 37, but Sheriff Burns said half the people in his law enforcement section have not attained five years' experience.

"Don't get me wrong," Chief Goss said. "It is good to be a young department. New people are doing what they need to do, but they could be more prone to make rookie mistakes, and we have to be on guard for that, to pay attention."

To deal with that, he said, he has split up this year's seven rookies in the three shifts, two in each of two tours and three officers in a third shift. That in itself is not so unusual, he said, but to ensure a blend of experience and youth, some senior officers have been asked to delay a seniority privilege, the right to select the shift they work.

"I think everybody understood the rationale," he said. "We asked for volunteers, and we didn't have to order anybody."

Those who waive a shift move get the benefit of claiming their preferred days off, he said.

Sheriff Burns said he does not have that luxury with his senior people.

"Contractually, we are bound to put jobs up for bid," he said.

He has four new deputies. Two are on the day tour, and the other two are on nights. His department works 12-hour shifts.

"The biggest impact for our department is on special units, like SERT (Sheriff's Emergency Response Team)," Mr. Burns said. "I'd prefer to have our more experienced people there. They are more levelheaded."

None of his young officers have military experience, he said. "We tell them that we are a paramilitary organization, and that there are protocols and chains of command. They have to deal with that."

He added, "I've got guys on the road who haven't been to a fatal accident. If you are first on the scene, that can be pretty scary. Things like that you can't teach at the academy."

The sheriff looked three years ahead to when his department could take on an even younger appearance. He has two people who are eligible for retirement now, and in 2011, that number rises to 11, he said.

Both department heads said they are confident in the experience level of their shift leaders. Chief Goss said his youngest sergeant is a 10-year veteran, while the youngest sergeant with the Sheriff's Department has been on the job eight years.

Chief Goss said this "youth movement" should not cause too much concern.

"The young people want to do a good job, and they are doing a good job," he said. "Their decision processes may be a little different from the veteran. Is that bad? Not necessarily."