As the trial of the killers of a pro-Solidarity priest enters its final stretch, more questions than answers remain about the motives behind the sensational crime and its ultimate instigators.

Expectations that the court hearing might expose a high-level conspiracy of police or communist party officials against the Polish leader, Gen. Wojciech Jaruzelski, have faded. The main party daily, Trybuna Ludu, concluded this morning that the evidence indicates that the four secret policemen on trial acted alone.

In Torun's provincial courthouse today, apolice general, Zenon Platek, director of the department where the accused agents served and the highest ranking official scheduled to testify, said he had not known of the operation beforehand and would have prevented it if he had.

Although the perpetrators said in court they had assumed that the killing of the Rev. Jerzy Popieluszko had been authorized by higher-ups, they could offer no proof of high-level complicity and backed away from suggesting that top officials were involved.

The most senior official in the dock -- Col. Adam Pietruszka, a deputy department director charged with aiding and abetting the three junior officers who killed the priest -- has denied ordering the action or even knowing what his men were up to. No one has corroborated allegations by the killers that the colonel incited the slaying during meetings at the Interior Ministry.

But testimony by ministry employes last week and today implicated Pietruszka in an attempted cover-up, revealing that he censored damaging references to himself in reports by two ministry staff members. Other witnesses indicated that the colonel had been aware that his subordinates were on a mission Oct. 19, the day Popieluszko disappeared. He was told by his driver that they had taken the colonel's "W" pass, exempting them from searches by traffic policemen.

Is Pietruszka lying, or could the three junior agents have misread his instructions about how to deal with Popieluszko? If the colonel is not telling the truth, who, in turn, could have instructed him to eliminate the priest?

Another mystery is why the abduction was handled so unprofessionally and ended in such an amateurish killing. Was the death an accident, as the perpetrators have claimed, saying they had intended merely to frighten the priest but were panicked by a series of mishaps into killing him? Or was it premeditated, as suggested by disclosures in court that the possibility Popieluszko would die was discussed beforehand?

From his testimony it is clear that the chief plotter, ex-captain Grzegorz Piotrowski, hated the outspoken cleric and was deeply resentful of concessions granted by the government to Poland's Roman Catholic Church.

Piotrowski viewed the police leadership as impotent and indecisive in curbing church privileges and alleged illegal activities. Is it conceivable that he was driven by emotion to take the law into his own hands? Would an ambitious, 33-year-old section chief who had risen fast and was respected by colleagues have jeopardized a promising future by acting without orders or flubbing so crucial an operation?

Piotrowski is the most intriguing figure in the courtroom. A masterful performer, his moods have varied from arrogance and anger toward clerics to remorse and compassion toward the two lieutenants, now on trial with him, whom he recruited for the mission.

How can he behave with such aplomb facing a possible death sentence? Have hints been dropped to him not to worry? If so, by whom?

No one has made the connection in court, but meetings held at the Interior Ministry in September to discuss restraining Popieluszko coincided with an article in the Soviet newspaper Izvestia attacking the Polish priest. Was there a Soviet secret police link to the defendants and the crime?

For all its lingering questions, the court hearing has gone far in exposing the character and methods of those who work in one section of the country's hidden and dreaded security apparatus. Confirming long-held suspicions, the Interior Ministry has been shown to be a place of plotting and intrigues, of dirty tricks and political warfare against those who hold views out of step with the leadership.

It is an institution that, although sworn to uphold the law, has fostered in some agents a disregard for legal methods and a lack of understanding of political compromise. It is an institutional caste with special privileges often passed on from father to son. Two of the four defendants are offspring of secret policemen.

Piotrowski has attempted to widen the trial into an indictment of Popieluszko's pro-Solidarity activities and of alleged illegal behavior by other clergymen. Many Poles suspect that one reason Jaruzelski agreed to publicize the proceedings was to air unproved charges against the slain priest. The presiding judge, Artur Kujawa, has appeared eager at times to read into the record allegations about Popieluszko's alleged political plotting.

But confronted last week with protests from attorneys representing Popieluszko's family, who argued that such evidence was immaterial to the case and unsubstantiated, the court rejected a move by Piotrowski to elaborate a list of antichurch charges.

Was the panel of judges responding then to instructions from political leaders in Warsaw senstive to church interests? Are competing political factions in Poland's communist leadership intentionally reflected on the bench? Is the hard-line Kujawa, for instance, meant to balance Judge Jurand Maciejewski, who has kept the case focused on the police and won acclaim for his aggressive cross-examination?

The trial has dominated casual conversation in Poland since it began Dec. 27. The experience has been humiliating for the police but is widely seen as bolstering the position of Jaruzelski, who is given credit for applying the law against his own security establishment.

Jaruzelski has reasserted control over the police and the country, but at the expense of holding the security service up to a glaring public spotlight. Another veil has been stripped from the communist establishment. What this boost to Poland's political consciousness will mean in the long run is perhaps the major question as the trial nears its end.