The reason Joseph Pennington, a career violent criminal, was able to shoot a police officer in the leg after robbing a Queens bank recently, as prosecutors allege, and after having been convicted of seven felonies is that the law that would have sent him to prison for a longer period only counted two convictions.

Pennington, 43, was sentenced to prison twice in the 1990s for armed robbery sprees across the city, but the state’s persistent offender law counted each bundle of felony charges as a single count. If someone completes two separate violent felony sentences of more than one year in prison, a third felony conviction will carry a mandatory 20-years-to-life sentence, the president of the New York District Attorneys Association, Michael Bongiorno, said. It’s New York’s version of a “three strikes and you’re out” law. If convicted on charges of bank robbery and assaulting a police officer, Pennington could spend the rest of his life in prison. Legal experts said New York State’s laws are among the stronger ones that deal with persistent felons around the country, but Pennington’s case presents an example of the law’s shortcomings.

Pennington committed his first felony armed robbery in 1990, and then two more in 1991, law enforcement sources said. He was also charged with possession of a deadly weapon and grand larceny in the fourth degree. A judge sentenced him to three to nine years at Elmira Prison for the charges. He served three years.

Just four months after he left prison in 1994, he was charged with another two felony armed robbery charges in Queens. He was convicted and sentenced to Downstate Correctional Facility for a term of six to 12 years.

During his 11 years and six months there and at Sing Sing Correctional Facility, he completed a drug rehabilitation program, worked in an industry-training program, and did work as a porter, a spokeswoman for the New York State Department of Correctional Services, Linda Foglia, said. He had just two tickets for misconduct — both for fighting — during his whole stay. He was, by most indications, a good prisoner, Ms. Foglia said.

Pennington was released back into the city in January 2006. After that, he completed a drug test, was subject to a curfew, and met regularly with a parole officer, a spokesman for the state Division of Parole, Scott Steinhardt, said. Once again, Pennington appeared to be following all the rules for an ex-convict to re-enter society. But three weeks after his last parole meeting, he and another former Sing Sing resident, Dion Mines, 35, completed another bank robbery, according to a complaint filed in court by federal prosecutors. This time, though, a plain-clothes police officer stopped them, taking a bullet in his leg in the process.

Mines was released from Sing Sing in February 2006, a month after Pennington. Mines had served 15 years and 10 months of his 16 year sentence for manslaughter. At the age of 19, Mines killed a 14-year-old boy by shooting him in the mouth after they had a dispute over a moped in the Corona section of Queens, according to an article that appeared on August 3, 1990, in the New York Times. He had a less quiet stay in prison: Over the course of the sentence, he had 59 tickets for misconduct, including fighting, possession of contraband, and assaulting a corrections officer, Ms. Foglia said.

Pennington and Mines entered an HSBC Bank at 87-03 Queens Boulevard in the Elmhurst section of Queens at about noon on December 30, according to the federal criminal complaint. Wearing ski masks over their faces, the men each went to tellers on the opposite side of the bank, the complaint says.

Pennington pulled out a handgun and pointed it at the teller, the complaint says.

“Give me all the money. Fifties and hundreds,” each said to the teller, the complaint says. They made off with about $14,900; the stash also included two dye packs. When they returned to the street, they tried to hijack a Suzuki Grand Vitarra, but the driver sped away, the complaint says. Then, according to the complaint, they tried to steal a Dodge Intrepid, but unbeknownst to them, the driver was a New York City Police Officer, John Lopez.

When they realized he was a police officer — there was a red siren on the floor of his car — they tried to get away, firing at him as he trailed after them on the avenue, the complaint says. Officer Lopez was hit once in the leg, but he managed to take down Pennington with a shot to the torso, the complaint and police officials said.

Pennington remains in critical condition at Elmhurst Hospital, and Mines has been remanded to federal detention until a future hearing. An attorney for Mines did not return phone calls last week. “Pennington typified the threat to our officers: an armed felon who didn’t hesitate to shoot a police officer,” the police commissioner, Raymond Kelly, said in a statement. “That willingness to shoot at police is all too common today. Officer Lopez exemplified the courage displayed by our officers, off duty and on.”

In New York the debate over whether stricter laws should be passed to stop repeat offenders has quieted down as criminal justice experts and legislators have increasingly approached the problem of recidivism from the perspective of “prisoner re-entry.”

The executive director of the Public Policy Program at the Correction Association, Robert Gangi, said one problem with the debate over prisoner re-entry is that every prisoner has a different story with his or her own unique problems.

“People do turn their lives around, particularly people who come out of prison as old as this guy is,” Mr. Gangi said. “Each case is different: personal motivations, personal demons, personal histories.”

A senior fellow at the Manhattan Institute, John McWhorter, said the answer to recidivism is not likely to be found in longer prison stays, a technique which hasn’t shown much promise over the years.

“The obstacles that people face when they leave prison can be pretty intimidating,” Mr. McWhorter, said. “It can be very hard to find somewhere to live — sometimes they have no high school education, job skills, or an untreated substance abuse problem … It shouldn’t be surprising that under the current situation, people who leave prison end up going back to prison.”

A report by the Independent Committee on Reentry and Employment released in November said that of those arrested one year after they were released from prison, 60% are unemployed, and of those who violate their parole or probation, 89% are unemployed. The report, which was commissioned by Governor Pataki’s state criminal justice coordinator, Chauncey Parker, called for a statewide Commissioner of Reentry and a wage-subsidy program to get businesses to hire formerly incarcerated people, among other changes.