A state prosecutor today demanded the death sentence for a former secret police captain accused of slaying a pro-Solidarity priest and sought jail terms of 25 years for each of the other three Polish security agents charged in the crime.

In concluding remarks, chief prosecutor Leszek Pietrasinski ruled out the involvement of other Interior Ministry officials in the killing of the Rev. Jerzy Popieluszko, but suggested that an ongoing investigation into the existence of possible accomplices may yet implicate western "centers of subversion" in the priest's death. Such groups, he observed, have benefited from the tragedy, which has rocked Poland as no other event since the crushing of the independent Solidarity union movement.

To the shock of Popieluszko's family, Roman Catholic Church officials and many other Poles, the prosecutor also sharply criticized the slain cleric, accusing him of provoking his own killing by failing to refrain from antistate activities. The prosecutor equated what he called Popieluszko's "extremist attitude" with that of his killers, saying both sides saw themselves as above the law.

The prosecutor drew on what has been a persistent undercurrent in the trial, now in its 22nd day, involving numerous allegations of corrupt, immoral, improper and subversive activity against Popieluszko and other Polish clerics.

Such charges have been raised at the hearings, often with the enthusiastic support of the presiding judge, ostensibly to support the lead defendant's claim of a political motive for the crime -- that is, his frustration at the government's inability to curb illegal church behavior. But many Poles suspect the attacks reflect an attempt by the communist leadership to balance the humiliation that the security apparatus is undergoing in the unprecedented public prosecution of four of its own.

Summarizing the state's case, the prosecutor cited Grzegorz Piotrowski as the leader of the Oct. 19 murder. He described the 33-year-old ex-captain as "a cold and cruel criminal" full of "false regrets" who has "adopted a protective coloring of a chameleon and who is pretending to be a sensitive and law-abiding person."

He portrayed the two ex-lieutenants, Waldemar Chmielewski, 29, and Leszek Pekala, 32, also accused of the killing, as youthful, intelligent and committed police agents who were misled and "exploited as instruments" by Piotrowski, who took advantage of their respect for him. The prosecutor said the two men, because they had shown remorse and had cooperated with investigators, should be spared the death sentence.

The prosecutor also said that without the instigation and assistance of the fourth defendant, ex-colonel Adam Pietruszka, formerly deputy director of the Interior Ministry department where the three junior-ranking policemen served, the murder would have been "completely impossible."

Rejecting Pietruszka's protestations of innocence, the prosecutor said that two documents signed by him -- a travel order authorizing his men to go outside Warsaw on the day Popieluszko was killed and a special pass exempting the agents from search by traffic policemen -- implicated him, and his guilt was confirmed by his vain efforts to cover up the crime.

The prosecutor called the grey-haired Pietruszka "the most cynical of all the accused" and said the only extenuating circumstance in his case was that he was not at the scene of the killing.

Polish law does not provide for life imprisonment. The maximum penalty is death by hanging. The second most severe is 25 years in jail. All four defendants were stripped to the rank of private and fired from their Interior Ministry posts after their arrests.

Popieluszko, a defiant champion of the Solidarity movement, was abducted on the night of Oct. 19 north of Torun, beaten senseless by his captors when he tried to flee from the trunk of their Polish-made Fiat, then bound with a noose around his neck and dumped, with a bag of stones tied to his feet, in a reservoir on the Vistula River at Wloclawek.

The perpetrators claim they had intended only to kidnap and frighten the Warsaw priest into revealing underground contacts and stopping his anticommunist sermons, which were attracting large crowds.

But deputy prosecutor Zygmunt Kolacki, participating in today's summation at Torun's provincial courthouse, noted that the police agents made elaborate preparations before the killing and took with them gagging materials, rope and sacks full of stones. "They had nothing in the car which could have helped the priest to live," he stated. "They did everything in their power to take his life."

Shifting to an attack on Popieluszko and the church, chief prosecutor Pietrasinski said the priest had conducted a campaign of hatred against communist authorities while Roman Catholic officials had shown "excessive tolerance for the violation of religious freedoms" by Popieluszko and other outspoken priests.

He quoted fragments from the state's indictment against Popieluszko, which was dropped last summer under a broad amnesty, mentioning material discovered by police in a December 1983 raid on the cleric's apartment -- including 11,000 underground leaflets, three tear-gas grenades and two packs of explosives. Popieluszko said the items had been planted.

The prosecutor argued that the priest and his killers were two shades of a similar phenomenon, asserting that both parties opposed the government's accommodation with the church and other policies aimed at reducing conflict and social tension.

"The extremist attitude of Popieluszko gave birth to an equally harmful extremism which produced this very crime," he declared.

Echoing statements by Polish leader Gen. Wojciech Jaruzelski, the prosecutor termed the killing a political provocation. He said it was "not a coincidence" that it occurred a week before a meeting of the Polish Communist Party's Central Committee, implying that the death was somehow meant to trigger a leadership crisis and renewed crackdown.

He said the killing coincided with the "intensification of a propaganda campaign against Poland" by such western groups as U.S.-financed Radio Free Europe and the Paris-based Polish emigre journal Kultura, intimating that these or like-minded organizations may have been behind the crime.