A horde of television crews and newspaper photographers recorded the accuser's trip into the police station, making it clear from the start that the prosecution of Shanley would be different than the typical sexual assault case. It was an early signal that the case would be a challenging one for authorities.

Though most alleged victims of sexual assault come forward quietly, the accuser and three other former altar boys from St. Jean the Evangelist Parish who made allegations against Shanley that spring were already very much in the public eye. For months, they had been at the center of a huge civil lawsuit a powerhouse Boston law firm brought against the Boston Archdiocese seeking compensation on behalf of hundreds of alleged sexual abuse victims.

That sequence -- the civil case first, and the criminal case afterward -- was unusual. And, according to legal specialists, it has been damaging to the prosecution.

The vast majority of alleged victims in sexual assault cases wait until after the criminal case is resolved before seeking damages in a civil lawsuit. Legal observers said the reverse order in the Shanley cases -- the accusers settled their civil cases last year -- has severely undermined the prosecution against Shanley, who is scheduled to go to trial tomorrow in Middlesex Superior Court in Cambridge.

The order of the cases has caused several complications for Middlesex prosecutors: repeated delays in the start of the trial, the civil litigation generated hundreds of pages of documents and statements from the accusers that Shanley's attorney has already begun using to attack their credibility, and the civil settlement raises defense questions about the accusers' motive in coming forward.

''It's the difference between a defense attorney conducting a cross-examination on someone based on a two-page police report or a 500-page [civil] deposition," said Boston College Law School professor Michael Cassidy. ''If you were a defense lawyer, which would you rather have?"

More fundamentally, having civil cases precede criminal ones, lawyers said, has allowed Shanley's attorney, Frank Mondano, to aggressively press the defense's strongest argument: that the accusers are motivated by financial gain rather than a quest for justice.

''If they [accusers] even show interest in a civil case, it is bound to affect how they are evaluated [by a jury]," said Martin Murphy, a former state prosecutor who now works as a defense attorney.

Neither Middlesex District Attorney Martha Coakley nor Mondano would comment on the upcoming criminal trial.

The most visible sign of the weakened criminal case against Shanley is that the prosecution is now expected to hinge on just one accuser instead of the original four.

Although it is commonplace for alleged victims of sex crimes to decide not to go to trial, legal specialists said that a mutual decision by prosecutors and two of the four victims to withdraw from the case last July was probably influenced by the fact that the criminal case has dragged on for 2 years -- a full year longer than average -- while the civil case played out.

''Because of what happened to them, victims of crime are often troubled people who are going to get buffeted around by life," Murphy said. ''The longer a case goes on, the more likely it is that something is going to happen to make them change their mind about going forward. The criminal justice system wears people down."

A third accuser was questioned so aggressively during a pre-trial hearing last year by Shanley's attorney that he chose to drop out of sight rather than face a second day on the witness stand. That accuser, who has battled substance abuse and homelessness, is also expected to be dropped from the case before it goes to trial, lawyers on both sides of the case have said in court.

The pressure on the final accuser, meanwhile, has become so great that he has asked media outlets not to publish his name or take photos of him or his family. In a Jan. 10 letter to the media, he wrote that he had just been married and had started a new career, and that it would be ''difficult if not impossible for me to go forward with the criminal trial if I am identified publicly."

The Globe does not publish the names of sexual abuse victims without their consent. Middlesex Superior Court Judge Stephen Neel, the presiding judge, ruled Friday that neither the accuser, his wife, nor his father could be photographed during the trial.

The lone remaining accuser is expected to face tough questioning about how and when he remembered the alleged abuse by Shanley.

Shanley, now 73, was initially charged with 10 counts of child rape and six counts of indecent assault and battery, and has been free on bail while awaiting trial. He denies that he ever raped anyone. He was a self-described street priest during the 1960s and 1970s, when he developed a ministry helping troubled youths. Internal church records showed that church officials were aware of sexual abuse complaints against Shanley as early as 1967 and had received reports that he advocated sex between men and boys, but they continued to transfer him from parish to parish. Shanley was arrested in San Diego in 2002, and defrocked last year.

Because of the two-year statute of limitations in civil tort law, the accusers could not have even brought civil cases if they had not said that they had repressed their memories of Shanley and only recovered them when the clergy abuse scandal made national headlines a few years ago.

The statute of limitations in criminal cases operates differently, however. Shanley is one of the few priests from the scandal who could be prosecuted, because he left Massachusetts for California in 1990. That stopped the clock on the 15-year criminal statute of limitations.

Prosecutors were unable to bring charges based on more than a dozen alleged victims who said Shanley abused them in the 1960s and 1970s, but the charges based on the Newton accusers could be brought because the alleged conduct occurred during the 1980s.

Both civil lawyers for the accusers and Middlesex prosecutors have defended the validity of repressed memory, but Mondano is expected to make a major issue of it at trial. He is expected to call Elizabeth F. Loftus, a University of California at Irvine professor and co-author of a book called ''The Myth of Repressed Memory," as a defense witness in an attempt to undermine the final accuser's credibility.

Former Essex district attorney Kevin Burke said repressed memory is ''a major issue" for prosecutors.

''As a prosecutor, it is a situation you wish you just didn't have," said Burke, now in private practice. ''In the minds of the jurors, it has an effect on how they view anyone's credibility."

Mondano has already challenged the final accuser's repressed memory on other grounds, arguing in court recently that documents from civil lawyers at Greenberg Traurig introduced in the case suggest that the accuser had a relationship with the law firm before he said he recovered his memories. Greenberg Traurig partner Robert Sherman disputed that claim, saying that a paralegal mistakenly put the wrong date on a fee agreement contract reached between the firm and the accuser.