The Boston Police Department plans to bolster homicide squads in the coming year and examine the way it investigates killings in an effort to combat one of the city’s most intractable problems: the painfully slow rate at which most slayings are solved.
The plan is not finalized, but an initial proposal calls for each homicide squad, which is now made up of two detectives and a sergeant, to be beefed up by two more investigators and to be supervised more closely by commanders. Detectives from the drug and gang units would regularly be called to crime scenes to help.
In addition, DNA specialists who study forensic evidence at crime scenes would receive more intensive training, and the Secret Service would be asked to help retrieve phone records more quickly.
The homicide squads will receive the extra resources for 18 months. Then, analysts plan to compare the department’s clearance rate - the proportion of cases in which a suspect is arrested or identified in an arrest warrant - to previous years. They will also compare Boston’s success rate to that of other cities to determine whether the additional manpower helped investigators close more cases more rapidly.
If the clearance rate rises, the department would continue using the extra resources.
“For the next year we’re going to be really focused on the issue of shootings and homicides,’’ Commissioner Edward F. Davis said in interview. “I really want to try and work on holding people accountable for it.’’
The city is launching the initiative amid a dip in overall violent crime.
Compared with 2010, major crime in Boston dropped 8 percent this year, and killings fell 14 percent, according to preliminary figures from police on Dec. 26. the most recent data available.
But the murder-clearance rate continued to stagnate: Boston police solved 23 of the 62 homicides, or 37 percent, that occurred in 2011. The national average usually hovers at more than 60 percent.
Meanwhile, the number of nonfatal shootings dipped slightly in 2011 to 260, from 263 in 2010, an especially violent year. Department officials said they were unable to provide the clearance rate for shootings.
The latest effort to improve the city’s clearance rate does not have a budget yet, but Davis said the department would dip into $2 million saved in 2010 through reductions in overtime to cover the costs. A $500,000 grant from the Department of Justice will bolster the effort.
It is not the first time the department has sought to strengthen the homicide unit.
In 2007, shortly after Davis became commissioner, he beefed up the unit to 25 detectives and added two more detectives to the cold case squad, for a total of three. He has replaced the deputy superintendent in charge of the unit three times.
Despite the changes, the percentage of homicides solved by Boston detectives has lagged. In 2010, the department solved 27 of the 72 homicides that occurred that year.
Department officials said they measure the clearance rate by the total number of homicides solved in a given year, regardless of what year the murder occurred. By that standard, the department had a clearance rate of 49 percent in 2010 and 53 percent so far this year.
Still, that is below the 60 percent rate Davis has said he wants to see.
Police say the nature of Boston’s homicides makes it particularly difficult to solve them: The majority tend to be the result of gang feuds or are drug-related, the kinds of cases that draw little cooperation from witnesses.
In the department’s successful grant application to the Department of Justice last August, police had proposed bolstering the resources of some investigative units while leaving others as they were. Then, police would flip a coin to determine which homicide was assigned to the bigger squad and which went to the traditional team.
The idea was scrapped three months later.
Davis said he worried about the reactions of families who learned their loved one’s case had been assigned the smaller detective squad.
“Everybody in the room was concerned about ethical implications of certain cases being treated differently than other cases,’’ said Anthony Braga, a professor at the Rutgers School of Criminal Justice who will be conducting the analysis for Boston police.
Braga said he also worried that detectives in the traditional squads would try to overcompensate for having fewer resources, making the final results unreliable. The relatively small number of homicides in Boston each year could not guarantee that any results were beyond reproach, he said.
In the end, department officials decided that all of the squads should receive extra resources. The entire homicide division, which now has 17 detectives and 10 sergeant detectives, will probably get bigger, though Davis said he is not sure how many more investigators would be added.
Police could also use overtime to assign more investigators to cases, he said.
“Quite frankly we’re willing to leverage the savings,’’ Davis said. “But a lot of these people are on-duty personnel. . . . I don’t think it’s going to be unwieldy.’’
Braga said he will look at both standards for measuring the clearance rate. He plans to compare the results with the rates of other cities and the department’s for the last 10 years.
Braga said he will also analyze the clearance rate of nonfatal shootings, which typically get considerably fewer resources than homicides. “The only real difference in a majority of these cases is whether someone lives or dies, but research shows that the intent [of the shooter] is the same,’’ he said.