Crime data released last month by the US Department of Justice (DOJ), along with previous years’ reports, shows that arrest rates for violent crime in Massachusetts have plummeted during the Mitt Romney–Kerry Healey administration. Most notably, the arrest rate for rapes has been barely half what it had been before Romney and Healey took office in January 2003.

The new figures could be particularly damaging to Healey, who has portrayed herself as the administration’s leader on criminal-justice and public-safety issues. The data could also weaken her authority to criticize Patrick for being soft on crime.

A Boston Phoenix analysis of the DOJ data shows that the arrest rate for rapes was 26 percent — just under the national average — in the three years before Romney took office, but just 14 percent since then. During the three years under Romney and Healey, 758 arrests were made for rape in the state, compared with 1361 in the previous three years. That’s 600 fewer rapists arrested. The total number of reported rapes in Massachusetts, meanwhile, remained the same, even as the national figure dropped by 10 percent.

During the same years, the arrest rate also declined sharply for the other three categories of major violent crime: the arrest rate for murder dropped from 48 percent to 26 percent; robbery, from 23 percent to 11 percent; and aggravated assault, from 48 percent to 29 percent.

State and federal officials contacted by the Phoenix were unable to determine why the statistics changed so drastically in recent years. “To my knowledge, there have been no significant changes in the reporting practices or the completeness of the data,” says Daniel Bibel of the Massachusetts Crime Reporting Unit, in Framingham.

The drop in arrests may be attributable, in part, to state budget cuts to aid for cities and towns, which have led municipalities to lay off police officers, suggests Brandyn Keating, executive director of the Criminal Justice Policy Coalition in Boston, which advocates for sentencing and Criminal Offender Record Information (CORI) reform. The DOJ data shows that 16,286 police officers were working in the state as of last October, up slightly from 2004 but still 400 fewer than the 2001 high.

“It follows that if you have less police, you will have less arrests,” Keating says.

Springfield, which has been under severe budget limitations, had 106 fewer police officers in 2005 than in 2002, according to the DOJ report. The Boston area has also been hit hard, losing 68 officers in Boston, 20 in Somerville, 15 in Medford, and 10 in Lynn.

Arrest rate for violent crimes, Massachusetts

Crime rates in Massachusetts (per 100,000 population)