Jim Mingle and Mike Boyd, detectives for the Baltimore Police Department, usually work in ties and jackets, but as daylight wanes on this day, they are standing on a West Baltimore street corner in their uniform blues.

"Still fits," Mingle says, patting his stomach.

Mingle and Boyd are looking out over a sidewalk in the 1700 block of Walbrook Ave., a long, straight street lined with two-story rowhouses. The late afternoon seems calm, and kids play basketball on the sidewalk just a few houses from them. But police radios on the detectives' belts soon crackle with news of a stabbing several blocks away.

On this 6 p.m.-to-2 a.m. shift, the detectives' main role is not investigating crime but preventing it, beefing up patrols to take back Baltimore's streets in the face of a rise in shootings and homicides, up more than 30 percent over last year.

Boyd and Mingle are assigned to West Baltimore, which has seen 15 killings this year, including a triple homicide this week. Along with 150 sworn officers who typically work administrative jobs, detectives are being called upon this month to temporarily bolster patrol units and create a visible blanket over the city to smother the outburst of gunfire. Police take turns in the new role: Boyd and Mingle worked the beat Wednesday; another set of officers was to be rotated in Thursday.

While some blocks are assigned one officer on foot patrol during this crime-fighting initiative, the assignment of two officers — especially detectives, who usually seek out sources and study trends — speaks to the trouble in the 1700 to 1900 blocks of Walbrook.

This month, a man was killed across from a church on those blocks, and the bodies of a couple were found late last month executed in a burning car nearby. Baltimore police have been called to the blocks more than 300 times in the past year, according to police records.

The blocks are part of West Baltimore's Greater Mondawmin neighborhood, where residents have a lower median household income than the rest of the city and homicide is the fifth-leading cause of death, above diabetes, according to the Baltimore City Health Department. The area falls in the Police Department's Western District, a three-square-mile area.

Boyd, who has worked in the district for four years, says station commanders used to answer phones by saying "Welcome to the Great Western District."

"It's the wild, wild West," Mingle says. "Always has been, as long as I've been here."

The assignment for Boyd and Mingle is one of the most basic and historic of police roles: beat cops, shepherds of the sidewalks. Police believe their mere presence as night watchmen will keep criminals away.

"That's what you hope," Mingle says. "You walk around. You let everyone know you're here, and you lock your place down."

As his shift begins, Mingle eats a candy bar, knowing that he may not have time later. The pair begin their patrol simply enough, by walking.

Up the sidewalk they go, past a man on crutches and a woman in a red fleece who tells the officers, "We need y'all around."

Mingle, 44, works in Internal Affairs after stints over his 19 years as a homicide and missing-persons investigator. Boyd, 36, has spent 17 years with the force and works as a detective in the Western District, investigating shootings.

Both men, large and sturdy, have children in high school or college. Mingle, who has a grandson and joined the force after serving in the Gulf War, can't wait for retirement — "me, my wife, my dogs and my hunting schedule." Boyd expects to be working on the force longer; he has twins in elementary school and a sophomore in high school whose college years loom.

Near a boarded-up rowhouse, a man wearing sunglasses, a hood and a Toronto Blue Jays cap watches a group of kids playing basketball with a soccer ball and a plastic hoop. Boyd and Mingle stop by.

"C'mon," Boyd tells one of the boys. "I saw you make it across the street."

A kid in a gray stocking cap and Old Navy sweatshirt walks up to the detectives. "How many homicides happened?" asks Tyrone Smith, 11. "I saw the news. Twenty-nine homicides?"

Boyd says he doesn't know. The detective tracks down the ball and hoists a shot. Soon, the officers are caught in a game with the kids, their gun belts jostling up and down as they try to block the boys' shots. Other kids see the commotion and pull up on skateboards and scooters.