PANAMA CITY (AP) _ Panama may ask the United States to extradite Manuel Antonio Noriega to face possible charges in a second murder case, the head of Panama's Supreme Court said.

Also Friday, the United States signed an agreement with the government of President Guillermo Endara to help train the fledgling police force, which replaced Noriega's Defense Forces that were defeated in the U.S. invasion a year ago.

Court President Carlos Lucas Lopez said Friday that Noriega, in a Florida prison awaiting trial on drug-trafficking charges, is suspected of involvement in the 1985 death of Huga Spadafora.

Panama's attorney general earlier asked the Foreign Ministry to request Noriega's extradition to face charges in a homicide case involving Maj. Moises Giroldi, who attempted a coup against Gen. Noriega's rule in October 1989.

The judge said the court has decided to hear charges against Noriega in the Spadafora case and could solicit Noriega's extradition from the United States.

Spadafora fought with the leftist Sandinistas against Nicaragua's Anastasio Somoza regime of the 1970s and was later a critic of Noriega in Panama.

He was killed and decapitated along the Panama-Costa Rica border. His attackers were never caught.

Then-President Nicolas Ardito Barletta in 1985 refused to open an inquiry into the case after the military, under Noriega, opposed it.

The court said it was also opening investigations into the deaths of Carlos Efrain Guzman Baules, killed in an anti-Noriega demonstration; of Marcos Alberto Rodriguez Justine, grandson of a former Noriega aide; and of Carlos Rodriguez Justine, grandson of former Col. Marcos Justine, a Noriega ally. Rodriguez was killed this year.

Panama filed a $6.5 billion damage suit against Noriega in U.S. District Court in October, claiming he took part in assassination, torture, drug trafficking, money laundering, embezzlement, sale of visas and passports and other abuses while chief of Panama's Defense Forces.

The United States and Panama signed an accord Friday providing U.S. training and support for Panama's struggling, new civilian police force. No cost was given for the program.

Vice President Ricardo Arias Calderon said the pact aims at establishing ''a civilian police force with a high level of professionalism that respects human rights and helps institutionalize Panamanian democracy.''

He and U.S. training program director Patrick Long signed the accord at a ceremony attended by U.S. Ambassador Deane Hinton.

Panama replaced Noriega's military police with a civilian law enforcement agency after Noriega's ouster.

The accord allows the U.S. International Criminal Investigation and Training Assistance Program to design police academies, provide police training and funnel equipment into programs, a U.S. Embassy communique said.

U.S. police and Army Reservists have tried to help Panama convert its corrupt 20-year-old military police system into an effective civilian one, but many members are military men still loyal to Noriega.

Bank robberies, store holdups and prisoner escapes plague the nation.

The new 13,000-member agency has half the budget of its 16,000-member predecessor, the Defense Forces.

Early this month, officers led by an escaped senior police chief took over the police headquarters for several hours, protesting their treatment by the government. They surrendered to U.S. and loyal Panamanian forces.