Almost anyone can operate a Medicare-licensed equipment supply company -- even a convicted murderer.

Guillermo Denis Gonzalez, convicted of second-degree murder in 1992 and released from prison in 2004, bought a Medicare-licensed healthcare equipment company two years later.

On Friday, the Hialeah man pleaded guilty in federal court to defrauding the government healthcare program by submitting $586,953 in false claims for supplies that were never provided to patients by his company, DG Medical Equipment, during 2007.

But that's the least of Gonzalez's problems. After the 65-year-old enters his plea in federal court, he's heading over to state court -- to be prosecuted again on a first-degree murder charge.

Last year, Gonzalez was charged with the slaying of Sergio I. Quintero, 58, of Hollywood in an argument over money.

Hialeah investigators gave this account of the events leading to Gonzalez's May 2008 arrest: Quintero was at Gonzalez's Hialeah home sitting in his kitchen when the convict ``became enraged'' and punched the jeweler. With a kitchen knife, he stabbed Quintero, then stabbed him twice more in the torso, according to an arrest report.

Gonzalez dismembered Quintero, while ``periodically'' crushing the corpse's face with a mallet, the report said.

Someone digging through trash found Quintero's left leg in a commercial trash bin in a warehouse alley. The rest of his body parts were found in six black garbage bags in three dumpsters on Hialeah's east side, police said.

``Gonzalez cut off Quintero's head, both legs, both arms, both hands and torso,'' Detective Jose Proveyer wrote in his report.

Gonzalez confessed to killing Quintero, Hialeah Police Chief Mark Overton said shortly after the 2008 arrest.

Back in 1991, Gonzalez was charged with first-degree murder in the slaying of Eduardo Oses, who was shot to death with a silencer-equipped gun during a money dispute at a Hialeah Tire Kingdom. Gonzalez pleaded guilty to second-degree murder in 1992 and agreed to spend 30 years in prison. He served about 14 years.

After his release, he eventually bought DG Medical for $18,000 in December 2006. The Miami company, incorporated six months earlier by Deborah Gomez, had already obtained a Medicare supplier license in September of that year, according to public records.

In 2007, Gonzalez misappropriated physicians' names for prescriptions and Medicare patients' numbers, according to Assistant U.S. Attorney Christopher Clark.

Gonzalez is an example of Medicare's lax oversight of Medicare operators in South Florida. The agency claims it regularly conducts criminal background checks on Medicare operators and disqualifies convicted felons -- but Gonzalez fell through the cracks.

Medicare, funded with taxpayer dollars, reimbursed Gonzalez's business $31,442 -- chump change by healthcare fraud standards in Miami-Dade.

Gonzalez's case isn't that unusual in the underworld of Medicare fraud.

After billing Medicare for a short period, equipment owners routinely sell their businesses to others or install straw owners -- without reporting ownership changes to the federal government. This enables them to collect big bucks over a few months without notice.

In a 2007 report, Health and Human Services Inspector General Daniel Levinson took Medicare to task for failing to screen medical equipment applicants for criminal backgrounds, conduct regular site inspections and ensure basic operational standards.

In an assessment published last year, Levinson concluded that Medicare had not completed his recommendations to fix the glaring problems in South Florida's medical equipment industry.

In his words, they were ``unimplemented.''

Critics both inside and outside Health and Human Services point to persistent flaws in Medicare's oversight: Until recently, almost anyone -- including convicted felons -- could qualify to become a Medicare provider because the agency's criminal background checks, though required by regulation in recent years, were spotty or nonexistent.

Medicare officials said that in late 2008 the agency was going to start conducting full background checks on selected medical equipment suppliers in areas with ``high fraud potential'' such as Miami-Dade.

Medicare's anti-fraud director, Kimberly Brandt, said in a previous interview that regulators now conduct those checks on medical equipment applicants in Miami and Los Angeles, the country's worst areas for healthcare fraud.

Miami Herald staff writer David Ovalle contributed to this report.