Louis Rodriguez, a lifelong thief, is costing California taxpayers a lot of money.

And so are others like him, aging criminals locked away for life or extended sentences who require expensive, ongoing medical treatment.

The state's expanding prison population and the increasing average age of its inmates appear to be key factors behind one of the most contentious issues facing California lawmakers. They are at odds over whether to approve $7 billion to build medical units for a prison health care system that has been ruled unconstitutional.

The money has been ordered by a federal court receiver who has been placed in charge of medical care in the state's 33 adult prisons.

Rodriguez is among those requiring pricey care.

He is serving a life sentence after being convicted of a "third strike" for stealing candy and cheese from a Los Angeles County grocery store. The conviction in 2000 followed another petty theft and a string of robberies nearly 30 years ago.

The 66-year-old inmate is in the California Medical Facility in Vacaville, coping with the final stages of terminal liver disease. Parole officials rejected his petition for compassionate release, so he most likely will spend the rest of his days in the prison hospice.

"For people who are old and feeble, hopefully we'll be left to die in peace," Rodriguez said. "I'm waiting for that phone call that says you can go home to die. That's all I got left."

Aging inmates cost two to three times as much to incarcerate as younger prisoners, an average $98,000 to $138,000 a year.

Between 1980 and 2007, the average age of California inmates increased from 27 to 37.

The prisons hold more than 22,000 inmates over age 50, or about 13 percent of the overall adult inmate population. In 1998, the number was 9,820, or 6 percent of the prison population.

Prison authorities say inmates age faster than the general population because of stress, a history of drug use, poor medical care throughout their lives and other factors. A 50-year-old inmate can have the physical and mental condition of someone 10 years older.

At the end of 2007, California housed 4,805 inmates age 60 and older, or about 3 percent of the prison population. A decade ago, that number was 1,951, or just more than 1 percent of all prisoners.

Prison populations nationwide also are aging.

The number of inmates 55 and older in state and federal prisons increased from 44,200, or 3.3 percent of the population, in 2000 to 80,200, or 5.3 percent, in 2006, according to the most recent statistics available from the U.S. Justice Department.

The California Department of Corrections and Rehabilitation expects its over-60 population to increase 80 percent by 2012.

That rise is due in part to tougher sentencing laws passed in recent years that send convicts away for longer stretches.

Some advocates say the state could save money by giving compassionate release to older, infirm inmates. A year ago, Gov. Arnold Schwarzenegger said he was open to releasing "the old, feeble and sick who pose no threat to the public."

The corrections department estimates that paroling all nonviolent offenders 55 or older, sick or not, would trim the prison population by about 1,000 and save about $20 million annually.

"We are paying the most amount of money to incarcerate those people who are the least risk to public safety," said Heidi Strupp, an advocate with the San Francisco-based group Legal Services for Prisoners with Children.

A proposal by state Senate Democrats would use existing compassionate-release laws to free more ailing inmates. Caring for a severely disabled inmate can cost the state $1 million a year or more, said state Sen. Mike Machado, D-Linden, chairman of a subcommittee that oversees prison spending.

The proposal would limit the releases to nonviolent offenders who have not committed sex crimes or serious offenses.

The debate over how to care ill inmates is connected to three lawsuits related to overcrowding in state prisons.

The 33 prisons house about 159,000 inmates but have a capacity of just about 100,000. Another 11,000 inmates are in fire camps or private prisons. Plaintiffs claim the crowding has led to poor medical, mental health and disability care for inmates.

If a settlement isn't reached, a special panel of three federal judges could order a prison population cap or other steps leading to the release of thousands of inmates.

The receiver appointed to oversee prison health care wants the $7 billion to build medical units for roughly 6 percent of the inmate population, or about 10,000 beds.

"Given the aging population in corrections and their health care status, we essentially need to build ... long-term housing for people who need long-term care," receiver J. Clark Kelso told a state budget subcommittee this spring.

Funding concerns have stalled Kelso's plan in the Legislature, which is struggling to deal with a projected $15.2 billion budget deficit for the current fiscal year.

Some actions to deal with aging prisoners are being considered independent of any court orders.

California corrections officials are turning the surplus El Paso de Robles juvenile correctional facility in San Luis Obispo County into a low-security prison for 1,000 nonviolent men over age 50. The conversion is starting this month.

Other attempts to ease the strain on older inmates are under way in the Legislation, but some of the steps could add to the already high cost of incarceration.

A bill by Sen. Sheila Kuehl, D-Santa Monica, would grant privileges such as easier work and bunk assignments to inmates over age 55. They also would get first call for meals and would not be required to drop to the floor during security alarms.

Prison employees would be trained to deal with inmates who may no longer be able to hear commands or might act out because of dementia. Older inmates would receive an identification card and an ombudsman to help with their complaints.

The bill stalled in the Senate Appropriations Committee, leaving its fate uncertain because Kuehl is termed out of the Legislature after this year.

Ultimately, the answer may be supervised release programs for most elderly inmates and minimum-security "prison nursing homes" with specially trained staff for the most frail, said Jonathan Turley, founder and director of the Project for Older Prisoners, an advocacy group.

"Older prisoners may be high risk for bad checks or forgery, but they're not high risk for escape," said Turley, a George Washington University law professor. "I mean, they're not going to throw their walkers over the razor wire."

Federal studies show that less than 5 percent of inmates 55 and older are likely to commit new crimes after their release. By comparison, about 70 percent of California inmates overall return to prison.