The mile-square city of South Tucson--home to 6,500 residents, mostly poor Hispanics--has filed for bankruptcy in the face of a $4.5 million debt to a paralyzed former policeman.

The dingy community, completely surrounded by Tucson, is believed to be the second municipality in the United States to file for such protection under Chapter 9 of the Federal Bankruptcy Act. The other was Wapanucka, Okla., population 470.

With an annual budget of $3.1 million, South Tucson officials have been less than anxious to pay a $3.6 million judgment awarded to former Tucson policeman Roy Garcia by a Superior Court jury in 1980. Interest has pushed the total to $4.5 million.

Garcia, now 33, was mistakenly shot in 1978 by a South Tucson policeman during a joint raid on a South Tucson home where a man with a shotgun was holed up. A bullet creased his spine, leaving Garcia paralyzed from the waist down, confined to a wheelchair.

Richard Grand, an attorney whose law firm stands to receive 45 percent of the award, accuses South Tucson officials of indulging in "expensive legal stalling." Says Grand: "City officials responsible for this injustice can walk away from it, but Roy can't."

"I'm angry," Garcia said, after learning of South Tucson's bankruptcy move. "They bought three years already. Now they're trying for more."

Enrique Sera, South Tucson city manager, says the bankruptcy petition, filed late last month, is having no effect on day-to-day operations.

If the court accepts the bankruptcy petition, a creditors' committee would be appointed, and the city would present a plan to the panel for paying its debts.

Garcia clearly was in a class by himself. The next largest debt owed by South Tucson is $105,000 to a cable television company. There are 86 other creditors, with five of them owed amounts ranging from $1,250 to $6,000. The rest are owed less than $750 each.

The median income for South Tucson families is about $10,000. Over the years, the city has been plagued by brazen prostitution and a string of sleazy bars, yet has remained proudly independent.

When it became clear last year that South Tucson would have to pay Garcia, a group of citizens circulated petitions aimed at disincorporating the city and making it a Pima County island within Tucson. The county would have inherited all of South Tucson's debts.

Some even thought that Tucson might decide to annex the town it surrounds, but Tucson city fathers weren't interested.

About four months after the shooting, Garcia--married and the father of two-- took a desk job with the Tucson Police Department. He quit six months later, complaining of bladder problems and almost continuous pain.

The forgotten man in the incident is David J. Novotny, 28, the South Tucson police officer who fired at Garcia. Although a jury cleared him of negligence, Novotny went through a state of deep depression afterward. Finally he quit the force and became a private investigator.