As a legislator, Mr. Guice was the primary sponsor of a 2011 law that set the state in a new direction. In addition to the quick dips and a related decline in probation revocations, the new approach includes the use of 90-day jail stays, still without formal revocation, for probationers with more serious crimes; efforts to focus probation and parole supervision on offenders judged at highest risk of trouble while easing the monitoring of others; and at least some oversight and services for those re-entering society after serving prison time.

Prison admissions have declined by 21 percent in three years, to 23,000 in the year that ended June 30, 2014, down from 29,000 in 2011, according to state data. The overall prison population shrank over the same three years to 38,000, and 10 prisons have closed, although significant further declines in prisoner numbers do not appear likely. The adult corrections budget, instead of rising as once projected, has dropped by $50 million per year, officials say.

“North Carolina demonstrates that there are ways to increase public safety while also saving a lot of money by shrinking the prison system,” said Michael Thompson, director of the Justice Center of the nonpartisan Council of State Governments. His group helped North Carolina devise the new approach and has promoted similar measures in several states, many of which have achieved modest reductions in prison populations.

Some of the savings here are being used to hire 175 more probation and parole officers to reduce caseloads. Their jobs have been redefined to focus less on catching miscreants and more on helping probationers break the pattern of crime by mandating services like behavior therapy, while imposing brief jail stints on those who drift.