Now, they are in daily legal combat in Courtroom No. 1 at the Dauphin County Courthouse in Commonwealth vs. Jay C. Smith.
There, as the murder trial of the former Upper Merion High School principal unfolds like a bizarre soap opera, the two men are advocates for opposite causes.
Guida, 38, trim and known for thinking quickly on his feet, is trying to cap a seven-year investigation by convicting Smith of the June 1979 slayings of teacher Susan Reinert and her two children.
And Costopoulos, 41, who has a measured, almost theatrical, presence before a jury, is fighting to save Smith from the electric chair.
"The stakes are high," acknowledged Costopoulos, 41, who, with his dark, swept-back hair and slightly pointed beard, is known for springing courtroom surprises that seem to have come straight from Perry Mason.
Guida, 38, who has dark-brown hair, dark eyes and a mustache, has a more low-key approach inside and outside the courtroom.
"I'm ready for anything," he says evenly.
Despite their differences in style, both men are regarded as excellent trial attorneys.
"Pound for pound, Rick is one of the most skillful prosecutors in the commonwealth," said Dauphin County District Attorney Richard Lewis, a former colleague of Guida's. "He is always extremely well prepared." And attorney Charles Rector, who is assisting in Smith's defense, said of Costopoulos: "He is to the courtroom what Mozart is to sheet music."
Since the trial began last week, Guida and Costopoulos have proven themselves aggressive courtroom fighters.
And Senior Judge William W. Lipsitt has made it clear that he would prefer a little less legal battling between the two men in his courtroom.
"Let's stop this," Lipsitt said with irritation as Guida and Costopoulos debated a legal issue during the testimony of one prosecution witness last week. "We are going to move along. This doesn't do the jury any good, and it doesn't do me any good."
But Guida has made it equally clear that he is not about to give up one legal point that he considers valid in a trial that is the climax of one of the most massive homicide investigations in Pennsylvania history.
Guida assumed control of the investigation in late 1981. For the previous 2 1/2 years, the best efforts of more than two dozen law-enforcement officers had failed to come up with sufficient evidence to make any arrests in the case.
Then, in November 1981, Attorney General LeRoy S. Zimmerman announced that his office would assume control of the case and review the mass of evidence that already had been collected in an effort to make an arrest or arrests. He assigned Guida to the case.
Seventeen months later, Guida convinced the statewide investigating grand jury that former Upper Merion teacher William S. Bradfield Jr. should be charged with plotting the killings so he could inherit Reinert's estate, including $730,000 in life insurance.
In October 1983, with Guida prosecuting the case, Bradfield was convicted by a Dauphin County jury of first-degree murder. He is serving three consecutive life sentences.
And now, Guida is attempting to convince another jury that Smith was Bradfield's accomplice in the slayings.
"I think this case is really a tribute to Rick," said Lewis. "I don't think, quite frankly, that many lawyers in the commonwealth could have pulled it together as well as he has."
Local lawyers familiar with his style describe Guida as an aggressive, thorough trial attorney especially talented at cross-examining witnesses and making complex evidence understandable for the jury.
"He has an excellent, very commanding, presence in the courtroom," said Dauphin County Prosecutor William Behe, who formerly worked with Guida in the attorney general's office. "And every question that he asks is asked knowing what's going to come out two questions down the road."
State Trooper John J. Holtz, who has worked side-by-side with Guida for most of the last five years, described him as a "cop's prosecutor" who works well with investigators and takes an active role in interviewing witnesses.
Born in Harrisburg, Guida received his undergraduate degree from Pennsylvania State University in 1969 and his law degree from Dickinson School of Law in 1971.
He spent three years in the district attorney's office - where one of his fellow prosecutors was Costopoulos - and five years in private practice before accepting a job with Zimmerman, his former boss in the district attorney's office.
Guida acknowledged that one aspect of the case that has kept him going through the years is the fact that two of the victims were children - Karen Reinert, 11, and her younger brother, Michael, 10.
"Anytime a child is killed, it's always a special case," said Guida, who
keeps two small photos of the children on the wall beside his desk. "All homicide cases are important, but the death of a child is particularly tragic."
And so, for the last several weeks, Guida has been working almost round- the-clock preparing for the trial.
"He's a human dynamo," said Kate Dreher, a deputy attorney general who is assisting Guida in the Smith prosecution, "He eats candy for breakfast, skips lunch and eats dinner if he thinks of it."
The Smith trial is equally important to Costopoulos, who entered the case eight months ago when Lipsitt asked him to accept a court appointment to represent Smith, who was unable to afford an attorney.
Costopoulos, though recognizing that Dauphin County would pay him a fraction of what a private client would pay him, eagerly accepted the case.
"I put the defense of Jay Smith very high on my list of contributions to what I have been trained to do," he said.
A defense lawyer for 15 years, Costopoulos is known for trying to cast suspicion away from his own clients by pointing an accusing finger at other possible suspects.
"He's like a master magician," said Skip Gouchenour, a private investigator who has worked with Costopoulos on more than 100 cases. "He has this way of making everything happen in a courtroom."
Born in Carlisle, Costopoulos graduated from Dickinson University in 1966 and received his law degree from Duquesne University in 1971 and his master's degree in law from Harvard University in 1972.
After a year as a deputy prosecutor, Costopoulos went into private practice so he could defend a cousin who had been charged with attempted murder.
And it was then, when his cousin was acquitted, that he got his first taste of victory.
"It felt real good," recalled Costopoulos. "I felt particularly good
because it involved a member of my immediate family."
A few years later, he won what, until now, had been the most celebrated case of his career when he defended an 18-year-old youth against charges that he killed his mother and disposed of her body in a shallow grave on a mountaintop near Carlisle.
But after the case was over, Costopoulos was charged with encouraging defendant Dennis Klinger and three other witnesses to commit perjury during the trial.
Although the charges were dropped, Costopoulos said the experience left a bitter taste for what he calls "vindictive prosecutors," who, he said, had been angered by his success in the courtroom.
"It was traumatic because it underscored that you can be charged and even convicted of a crime you never committed," he said.
For the last few weeks, Costopoulos has been devoting as many as 18 hours a day toward preparing for the trial.
"It's a physical, emotional and intellectual commitment," he said. "And the case doesn't leave you when you close the file."
In addition to the legal challenge posed by the Smith trial, Costopoulos has acknowledged that he also enjoys the media attention it has received.
After his first court appearance in September, for example, he passed out black-and-white glossy photos of himself to every newspaper reporter who wanted one.
But Costopoulos emphasized that his prime concern is his client.
"We do have an individual who is charged with the murder of a woman and the disappearance of her two children," he said. "He has maintained his innocence from day one, and he stands alone."