WASHINGTON -- An analysis of efforts to control violence by restricting guns says there is not enough evidence to reach valid conclusions about their effectiveness.
The National Research Council said yesterday that a major research program on firearms is needed.
''Policy questions related to gun ownership and proposals for gun control touch on some of the most contentious issues in American politics," Charles F. Wellford, chairman of the committee that wrote the report, said in a statement.
Among the major unanswered questions are whether there should be restrictions on who may possess firearms, on the number or types of guns that can be bought, and whether safety locks should be required, said Wellford, professor of criminal justice at the University of Maryland.
''These and many related policy questions cannot be answered definitively because of large gaps in the existing science base," he said. ''The available data are too weak to support strong conclusions."
Thirty-four states have ''right to carry" laws that allow certain adults to carry concealed weapons. But the report found no credible evidence that such laws decrease or increase violent crime.
The study also says no ironclad proof exists that Operation Ceasefire, a key part of the ''Boston miracle" in which the number of homicides dropped during the 1990s, made a difference in quelling youth violence. Operation Ceasefire threatened gang members with federal prison time, especially for gun crimes.
The dramatic drop in the youth homicide rate is compelling, the study says, but notes ''it is difficult to specify cause and effect."
David Kennedy, one of the Harvard University criminologists who helped design Operation Ceasefire, acknowledged the lack of definitive proof but said other cities that used similar approaches also cut crime.
''You get the same kind of large, sudden reduction in serious violence among young minority men in the hardest-hit neighborhoods," he said. ''And if you look at all the jurisdictions that have done this, it looks pretty persuasive that there's something real going on."
Boston Police Superintendent Paul Joyce said Operation Ceasefire was never viewed as ''the one component that would bring down the homicide rate."
''The reason we were able to bring violence down was our community policing, which included an enforcement component, an intervention component, and prevention. . . . No one agency, component, or strategy was responsible for bringing crime down."
Citing another example, the report said there is almost no evidence that programs aimed at steering children from guns have affected their behavior, knowledge, or attitudes toward firearms.
The report does not address gun policy, only the quality of available research data on firearm violence, control, and prevention efforts.
The report urges the development of a National Violent Death Reporting System and a National Incident-Based Reporting System to begin collecting data.
The study by the National Research Council, the operating arm of the National Academy of Sciences, was sponsored by the National Institute of Justice, Centers for Disease Control and Prevention, Joyce Foundation, Annie E. Casey Foundation, and the David and Lucile Packard Foundation.
Globe staff writer Suzanne Smalley contributed to this report.