As California struggles to meet a court-ordered reduction of its prison population, newly released figures show corrections officials overstated the number of low-level offenders eligible to be diverted to local jurisdictions as part of Gov. Jerry Brown's public safety realignment plan.

At issue are inmates who were being sent to state prisons for parole and other technical violations and became eligible to serve their sentences in county jails after Oct. 1, 2011.

Corrections officials long have argued that the churn of low-level felons in and out of state prisons was a major factor in overcrowding. Closing the revolving door to prison by sending those offenders to county jails instead - as envisioned under realignment - would be a major element in resolving the crisis, they said.

Speaking at a media event at Deuel Vocational Institution in Tracy in March, Corrections Secretary Matthew Cate put the figure at 47,000 offenders who had served terms of 90 days or less in 2011.

"Those guys were just going through our system so quickly, but they were keeping those beds full and crowding our system," he said.

Cate suggested that the drop in the prison population under realignment - more than 24,000 inmates to date - was largely due to placing parole violators and others under local supervision. Cate also said the state was "on track" to reach a June 2013 deadline set by a panel of federal judges to reduce the prison population to 110,000 inmates, or 137.5 percent of design capacity. The U.S. Supreme Court affirmed that order in 2011.

But according to data obtained by California Watch, the state Department of Corrections and Rehabilitation's estimate of the number of inmates cycling through the system was off the mark.

In 2011, 26,283 offenders were released after serving 90 days or less, a little more than half the number cited by Cate, according to a corrections department analysis.

What's more, the average daily population of parole violators being held in state lockups probably was not more than 19,000, according to Joan Petersilia, a Stanford University criminologist and expert on California's prison system.

"It's a much lower number than many people assume," she said.

Corrections spokesman Jeffrey Callison confirmed that the lower figure was accurate. "The 47,000 number was produced for the secretary and found to be in error," he said.

Cate resigned as corrections secretary late last month to become executive director of the California State Association of Counties. His last day with the corrections department is Nov. 11.

Cate said that under his tenure, California had reduced recidivism rates, increased rehabilitation services, cut spending and "ended the era of massive overcrowding," according to an Oct. 26 letter to corrections staff.

But according to new population projections [PDF], California likely will miss the deadline set by the court. The report estimated that the state inmate population will drop to 128,606 next year, about a 5 percent decrease from the year before and a significant change from the 2007 peak of 173,312, but not enough to satisfy the court order. (The current population includes 3,728 inmates in work camps not covered by the order and an additional 8,574 being housed in private prisons outside California. Corrections officials said they might postpone plans to return at least 4,000 out-of-state inmates to state lockups by the end of 2013.)

The report also estimated the inmate population would increase slightly, to 131,291 inmates, by 2018. It said one factor was local judges who are continuing to sentence some felons to state prison even though they qualify for jail terms under the realignment plan.

The panel of three federal judges has given California until January to outline a plan to meet the population cap, including considering a system to identify prisoners who might be candidates for early release.

Other options include legislative changes related to sentencing and earned credits and keeping inmates housed in facilities outside California. The annual cost of that program is more than $300 million.

But in court papers filed Sept. 17, state attorneys said California could provide adequate medical and mental health care for the current inmate population and would embark on an early release plan only "under protest."

They wrote: "Realignment has increased the potential dangerousness of inmates who remain in prison, making it uncertain whether it is still possible to identify remaining inmates who are unlikely to reoffend or who might otherwise be candidates for early release."