"Yo, Darnell there? This Donte.” Detective Richard Valenzia is speaking in a high, nasal voice, a voice that is not his own, a voice that is meant to sound like anything but that of a white cop. “No? Where he at?” Valenzia, sitting in the backseat of the unmarked white van, flips his cell phone closed. “Shit,” says the detective, reverting to his usual, deeper timber. “She said he just left the house.”

“Fuck,” Sergeant Seth Roussey says from behind the wheel as he swings the van around the corner, slowing to eyeball a group of young black men in hooded sweatshirts hanging out on the West Baltimore street. “The problem is there are so many goofs out,” he says.

Roussey and Valenzia work homicide and on this late, sunny November afternoon they are on the hunt. They’ve just narrowly missed finding their quarry—a reluctant witness needed for an upcoming trial—in a house where they know he’s been staying. Valenzia, by disguising his voice, had hoped to fool the woman who answered the phone into revealing the witness’s location. But she was unsure and now the detectives have to hope to find him out on the streets.

This is how Roussey, Valenzia, and the other detectives on Baltimore’s Homicide Operations Squad spend their days and often their nights. In Baltimore, as in many other large American cities, witnesses skip court dates—either out of fear or irresponsibility—with such regularity that prosecutors have taken to arresting them to compel their appearance. Many of these witnesses are hardly innocent bystanders: fully a quarter of the homicide witnesses the police are ordered to track down have an outstanding warrant for their own arrest for some other crime, which explains why many of them don’t want to be found.

Until 2002, Baltimore’s homicide detectives often had to waste precious resources and time trying to haul such uncooperative witnesses into court. Now the Homicide Operations Squad handles most of this work, freeing other detectives to work cases, look for clues and track down suspects. Every year since the unit’s founding, the number of witnesses it has been sent to find has increased, from 325 in 2003 to 375 in 2005. When I rode along with them in mid-November 2006, the unit was already looking for its 414th witness of the year.

The detectives assigned to hunt for witnesses go after their targets with the same zeal and using the same tactics that other homicide detectives use to pursue murder suspects—they ride in unmarked vehicles, stake out locations, search houses, interrogate friends and relatives, and even pay informants. “We have looked for people for a week solid, we’ve tracked their cell phones, staked out their place of work, and pursued them across the state,” says Lt. Brian Matulonis, who heads Baltimore’s Homicide Operations Squad. “We got that person, bring them in, and because we got the witness, [the defendant] took a plea.”

Sometimes the tactics are a tad unorthodox. One night Sergeant Alonzo Moreland and detective Byron Conaway—who, apart from Matulonis’ homicide squad, search for missing witnesses in non-fatal shootings and gun cases—are assigned to deliver a summons. Afraid to be seen talking to the police in her neighborhood lest she be branded a “snitch,” the witness has asked the detectives to meet her at work. This request is common. Merely to be seen talking to the police in many Baltimore neighborhoods can be dangerous. And even though Moreland and Conaway are both black, affording them a bit more anonymity in many Baltimore neighborhoods than a white detective would have, there is still a risk. What’s unusual in this case is where the woman works. She is a stripper on The Block, Baltimore’s notorious red light district.

While Moreland waits in the unmarked car outside on the strip club, the 31-year-old Conaway, wearing oversize hooded gray sweatshirt and jeans, flashes his badge to the bouncer guarding the door, enters, and climbs upstairs. Inside the dark club, with its pulsating lights and throbbing music, no one makes him for a cop. He has to shake off a bevy of scantily-clad women offering lap dances before he finds the woman he’s looking for. While she pretends to chat him up for a dance, he hands her the summons and tells her that she has to come to court. “All in a day’s work,” Conaway tells me with a smirk when we get back outside.

It’s a rare bit of comedy in a job that sees the detectives dwelling most often in the realm of tragedy. The same night the detectives’ work necessitates a visit to a strip club, I watch them escort a sorrowful 22-year-old black woman from her apartment. She had refused to answer her door until Conaway left her a message on her cell phone threatening to come back with a warrant and knock it down. Now she is going to jail—at least for the night. Tomorrow a judge will decide whether to hold her until she testifies at trial or set conditions for her release. It could be a long time before she’s home again: in one case in Baltimore, a 19-year-old mother of two who had failed to appear for court five times, spent more than five months in jail before a judge finally allowed her out on the condition she give a videotaped deposition.

In this case, the 22-year-old woman has also left behind two bewildered and frightened children; her father has said he’ll look after them until she’s free. The woman has begged the detectives, and they have agreed, to wait until she gets to the car before they cuff her. She doesn’t want to be humiliated in front of her neighbors. In the car, tears streak her face. The detectives ask why she missed her court date, where she was to testify against a former boyfriend who had held a gun to her head, threatening to kill her and her 8-year-old daughter. “I got a lot of phone calls telling me I was in trouble from his family and I was just scared,” she says in a meek voice, adding that she thought the taped statement she had given the police earlier would be enough. Moreland is sympathetic but tells her she has to come to court. “You can’t let them intimidate you to the point where you get yourself in trouble,” he says.

Moreland and Conaway say they often empathize with the witnesses they have to arrest. But the law is the law; without these witnesses in the court, Moreland knows, the prosecutors’ cases would collapse. As for empathy, it has its limits, as I discover when I ride along with Baltimore’s Homicide Operations Squad.

After cruising the streets for 15 minutes and failing to find their witness, Valenzia and Roussey decide to they will come back and hit the house where they believe he is staying early in the morning, hoping to catch him in bed. For now, they will move on to another target.

Along with Matulonis and Detective Frank Mundy, they stake out a West Baltimore house where they believe a witness and his family live. Through the front curtains, they can see lights on inside but no one answers the phone. The detectives, who are all white, are becoming impatient. They worry that some young men hanging out in a nearby yard may have spotted them and tipped off the man they are hunting. The detectives drive around to an alley behind the house and through the sliding glass rear door they glimpse figures watching television. They spring into action. After letting Valenzia off to guard the backdoor, they quickly drive around front again and park the van. Matulonis, Roussey and Mundy walk up to the front door and knock loudly. No one answers. The detectives pound on the door again.

Eventually a 20-something woman answers. The officers have decided in advance that they will not identify themselves as homicide detectives. Instead they claim to be parole officers checking up on the witness. They believe in this way they may be able to trick the woman into letting them into the house even if she claims the witness is not home.

The ruse works. Although the woman says the witness is not there—that she has not seen him in months—she lets the detectives in. The front door opens directly onto a small living room, where four small children race back and forth. In the back, two older relatives watch TV. The detectives say they need to look around. While Matulonis questions the woman, Roussey heads upstairs. The woman tells Matulonis that the man the detectives are looking for is the father of her children, but she insists he does not live there and that she has no idea where he is.

Within minutes, however, the woman is betrayed by her five-year old son, who has followed Roussey upstairs. Too young to have imbibed the Stop Snitching ethos, the boy doesn’t yet know well enough to lie to the police about where daddy lives. It turns out their witness does live there and has only recently left to go over to a nearby house. While Mundy guards the woman, the other detectives call for uniformed backup and race over to where the boy has said his daddy has gone. They surround that house, enter, and, while the occupants—one middle-aged woman and 10 children, ranging in age from toddlers to teenagers—are kept rounded up in the living room, search it. It’s too late though: their witness is not there.

Back at the first house, the detectives are furious. They claim they are going to charge the girlfriend with making false statements and impeding a police investigation. They cuff her and put her in the unmarked van. “Waste my fucking time, I’m gonna waste your fucking time,” Roussey screams at her. But in reality the woman is just bait: they tell her they might let her go if she can reach her boyfriend and convince him to turn himself in. “You’ll make a good hostage for us,” one detective says to her on the ride back downtown.

Once back at homicide, they stick the woman in an interrogation room. “If you help us, we’ll try to help you,” Matulonis tells her. She tries to reach her boyfriend on his cell phone. But he doesn’t pick up. She leaves a message telling him that unless he calls back soon, the officers are going to take her to jail. “If he really loves you, he’ll call,” Roussey tells her as she begins to cry. But the boyfriend never calls.