Armed robbers terrorized Oakland restaurants and small businesses in three separate crime sprees over the past year. The first wave targeted Asian eateries and struck during the 2007 holiday season. The second arrived last spring and was more indiscriminate. The third struck in July and August. All three made newspaper headlines and led television newscasts, shining a spotlight on the city's out-of-control crime problem and the Oakland Police Department's apparent inability to cope with it. In fact, the department's public response to the takeover robberies was both odd and illuminating.

The department's mantra for dealing with the city's crime spike has been: "We can't arrest our way out of this problem." Top brass has repeated this declaration in public meetings or whenever a reporter was within earshot, as if it were a common sense, widely accepted response to this sort of crisis. "Right now, it's pretty clear we are in a time of increased crime," said Deputy Police Chief Dave Kozicki, just before he summed up the department's official response to the Oakland City Council in April. "But the bottom line is we believe we cannot arrest our way out of these problems."

So instead of employing old-fashioned detective work to solve the restaurant robberies and arrest criminals, the department doubled down on a policing philosophy that it has employed repeatedly in recent years. It beefed up patrols and focused on so-called "hot spots." But this time it targeted the city's upscale shopping districts — and not the violent flatlands of West and East Oakland. It was an attempt at crime suppression, the security-guard approach to policing that the department successfully used to quell the sideshows several years ago. It's based on the premise that criminals are less likely to offend if they see a police car driving by. During the third crime spree, Mayor Ron Dellums even invited the Guardian Angels, a national vigilante group, to march around commercial districts in their red berets.

Yet the crime waves persisted, much like crime overall has remained at historically high levels in Oakland during the past three years. Then something interesting happened. Each crime wave abruptly ended when police arrested the perpetrators. It turned out that the department could arrest its way out of the problem after all. Each time police put the criminals behind bars, the takeover robberies stopped, the screaming headlines and breathless newscasts ended, and public fear faded away. People started patronizing restaurants again.

A closer look at the Oakland Police Department's response to the overall spike in violent crime that began three years ago reveals an agency with a policing philosophy that appears to have exacerbated the city's problems. An analysis of crime statistics by this newspaper reveals that Oakland's police department has the worst record in recent years among large cities statewide for solving violent crimes and homicides. In fact, Oakland's violent crime rate skyrocketed after the agency's ability to capture violent criminals fell off a cliff.

Oakland police once had a strong record for solving violent crimes and homicides, but during the three years since Police Chief Wayne Tucker took over the department it has solved less than one-quarter of the violent crimes and homicides in the city, according to figures from the state Department of Justice. The steep decline actually began under Tucker's predecessor Richard Word, and has worsened since 2005. And once the department's record for capturing criminals and putting them behind bars plummeted, the number of violent crimes citywide jumped sharply — 27 percent from 2005 through 2007 compared to the previous three years — far outpacing other large California cities.

Part of the problem is that Oakland's investigative unit is drastically understaffed. And the defeat last month of Measure NN — a parcel tax that would have paid for 180 new police personnel — will limit the department's ability to significantly expand its investigative staff anytime soon. But interviews and public records also show that there is much more to the department's crime-solving woes than a lack of investigators. Over the past few years, the Oakland Police Department has not made investigating crimes and capturing criminals a top priority — even as the city's crime rate soared to its highest level since the crack epidemic of the late 1980s and early '90s.

Oakland's homicide clearance rate — that is, the percentage of killings that the department solves — used to be impressive for a city with a lot of crime. From 1997 through 2000, it averaged 58 percent. But under Tucker, it has been abysmal. In 2005, his first year as police chief, the department solved only 12 of its 93 homicides, a clearance rate of just 13 percent. By comparison, the homicide clearance rates of other large California cities, such as Fresno, Long Beach, Sacramento, and San Francisco have remained fairly steady over the past decade.

From 2005 through 2007, the last year in which complete data is available, Oakland police only solved 86 homicides out of 357 total, or just 24 percent. In other words, since Tucker took command of the department, the perpetrators responsible for more than three-quarters of the killings in Oakland remain at large. "You want to get those folks off the street," said Franklin Zimring, a criminal justice professor at UC Berkeley's Boalt School of Law. "Twenty-four percent is very low."

By comparison, San Francisco has cleared 45 percent of its homicide cases in the past three years; Long Beach, 52 percent; Fresno, 67 percent; and Sacramento, 70 percent. The Express compared Oakland to those cities because they are the four closest in California in terms of population and demographics. The four cities also have similar homicide rates, although all are lower than Oakland's. We excluded Los Angeles, San Diego, and San Jose, the state's three most populous cities, because they're so much larger than Oakland and because both San Diego and San Jose have much lower violent crime rates.

Overall, the nationwide homicide clearance rate has hovered around 60 percent for many years. According to FBI uniform crime reporting rules, police agencies can't call a case "cleared" or solved unless they make an arrest and charges are filed. Exceptions include when a perpetrator dies before he's apprehended, a prime witness recants testimony after an arrest, or a suspect has fled the jurisdiction and cannot be extradited.