There is no evidence that the Brady law requiring background checks of handgun buyers reduced homicide rates after it went into effect in 1994, according to a study published Wednesday in the Journal of the American Medical Association.

The study's authors — Philip Cook, a professor of public policy at Duke University, and Jens Ludwig, a professor of public policy at Georgetown University — suggested that the reason the Brady law did not reduce homicides, most of which are committed with guns, was because it did not go far enough. The law requires background checks only for customers who purchased handguns from federally licensed firearms dealers and does not cover the large unregulated market involving an estimated 30 percent to 40 percent of all sales, like gun shows and private transactions, where criminals and juveniles often purchase handguns.

The study's conclusion was challenged by the Clinton administration, the Center to Prevent Handgun Violence, the gun-control group that helped push for the Brady law, and by other researchers who said the study was misleading and inaccurate.

James Johnson, the undersecretary for enforcement in the Treasury Department, said Justice Department figures have shown that crimes committed with handguns fell 52 percent between 1993 and 1998, which is twice the rate that crimes fell overall. The Brady law, new uses of tracing guns used in crimes by the Bureau of Alcohol, Tobacco and Firearms and other efforts directed at guns all led to the drop, Johnson said.

Douglas Weil, director of research at the Center to Prevent Handgun Violence, said the study was flawed because it only measured whether homicide rates in the 32 states, including Utah, that did not have background checks and waiting periods to purchase handguns before the passage of the Brady law showed a greater decline than the 18 states that already had such requirements.

To really gauge how much the Brady law reduced homicide, a study would have to look nationwide, Johnson said.