Any convicted criminal who spends time behind bars, either in a Mass. prison or county jail, would be subject to mandatory supervision after their release under legislation being announced Monday by Massachusetts Lt. Gov. Kerry Healey.

The mandatory post-release supervision is a key factor in an overall strategy by public safety officials and the governor's office to reduce recidivism by giving inmates more training while behind bars and more watchdogs when they get out.

The bill filed by Healey, who chairs the Governor's Commission on Criminal Justice Innovation, would ensure supervision lasting no less than nine months and up to 25 percent of the maximum sentence. The supervision would be imposed and the length determined at the time of sentencing.

The supervision would be handled by the state Parole Board or county probation department.

Mandatory supervision of former prisoners was among the key recommendations from two public safety commissions last year: Healey's own criminal justice innovation panel, and the panel headed by former Attorney General Scott Harshbarger, which conducted a nine-month probe into the state prison system after the cellblock slaying of defrocked pedophile priest John Geoghan.

Tough-on-crime sentencing laws created in the past decade have reduced the number of inmates released on parole. So prisoners finish their sentences, then walk out without anyone keeping track of them. That, the commission found, leads to higher rates of repeat offending.

In 1990, 65 percent of inmates were released on parole; that fell to 34 percent in 2002. The Harshbarger panel called on the Legislature to consider sentencing reforms and mandating post-release supervision.

Healey said her initiative would not cut prison sentences or let people out early.

"We're not saying we're going to get soft on crime," she told The Associated Press in a recent interview. "What we're saying is we'll expect honestly a lot more of the folks who are leaving our jails and prisons."

That could include, for example, keeping on medications or maintaining drug and alcohol rehabilitation.

"They're going to have to put up with a whole lot of meddling in their lives," she said. "But in return for that, the carrot is, the support will be there in a way that it hasn't been in the past."

For every 1 percent of recidivism deterred, Massachusetts would save $1 million, she said.