In times past, a yarn about fixing bets on horse races might be overrun with Runyonesque characters: wise guys outfitted in double-breasted suits and fedoras. Now, in perhaps the largest horse-racing scandal ever, three 29-year-old computer whiz kids once known for their khaki pants and topsiders, armed with little more than telephones and laptops, are accused of rigging a series of multi-race bets in an attempt to walk away with $3 million.

Chris Harn, Derrick Davis and Glen DaSilva, who became friends while members of the Tau Kappa Epsilon fraternity at Drexel University during the early 1990s, are expected to turn themselves in to authorities today at the U.S. Courthouse in White Plains, N.Y., after a three-week investigation by the New York Racing and Wagering Board, the FBI and the U.S. Attorney's office and others.

The U.S. Attorney for the Southern District has filed a complaint against the three, accusing them of conspiracy to commit wire fraud, which could result in five-year prison sentences, according to sources close to the investigation.

The three men have denied all wrongdoing.

"Many details of this investigation have apparently been revealed to the press but no one has addressed the issue that really matters," asked Daniel Conti, Harn's attorney. "What evidence is there that my client altered a bet?"

Three times last month, Davis and DaSilva made telephone calls to an off-track betting site in Catskill, N.Y., and placed automated wagers on a touchtone telephone on races being held at three tracks. The multirace wagers required Davis and DaSilva, who opened accounts at the Catskill facility weeks earlier, to correctly predict winners in either four or six consecutive races.

Because the computer system used by Autotote of Newark, Del., to process such bets can't handle such a large amount of data, betting information is delayed before being transmitted to the tracks. Authorities believe that Harn, then a senior software engineer at Autotote, took advantage of the delay by entering his company's computer system after some of the races had been run and changing the electronic bets by Davis and DaSilva to reflect winning horses.

In combination horse racing bets, bettors can wager on as many horses as they like, including the entire field, with the cost of the wager rising for each horse added. In the races Harn allegedly altered, Davis and DaSilva picked just one horse. But in the other races, Davis and DaSilva picked the entire field.

Authorities believe the bets by DaSilva on Oct. 3 at Balmoral Park, a harness track outside Chicago, and on Oct. 5 at Belmont Park, a thoroughbred track in Elmont, N.Y., were designed to test the betting scam. DaSilva won $1,851.20 in a Pick Four wager at Balmoral and $105,916 in a Pick Six at Belmont.

On Oct. 26, Davis called the OTB site at 2:13 p.m. and placed what racing sources said was $1,152 in Ultra Pick Six bets for the Breeders' Cup, a prestigious set of races at Arlington Park outside Chicago.

While more than 70 bettors correctly predicted winners in five of the Pick Six races, only Davis held a perfect ticket after the unlikely Volponi, the longest shot on the board at 43.50-to-1, won the final race, the Breeders' Cup Classic. Davis played the wager in a $12 denomination instead of the standard $2 denomination, which enabled him to collect a payout of $428,392 six times, plus consolation wagers for picking five of six races. He won more than $3 million.

Suspicions were raised immediately and the New York Thoroughbred Association asked the state racing and wagering board to investigate. Davis was told his payout was being held.

The scandal has left horse racing officials scrambling to protect the credibility of off-track betting, the process by which gamblers can wager on races run in other cities and countries often without leaving their homes. Off-track betting has become a critical revenue source for the $14.5 billion industry coping with declining attendance at tracks the past few decades.

That Harn was an apparently well-regarded employee of the largest of the three computer wagering companies that process the wagers makes the threat even more serious for the industry.

"There's never going to be fool-proof security," said Steve Surdu, director of consulting for Foundstone, a security firm based in Mission Viejo, Calif. "It all comes down to people. It's as old as the ages. There's always people willing to break the law."

In interviews with former fraternity brothers, other friends and former co-workers, the three are described as having formed a social bond while in college that centered as much on their love of computers as their love for parties. The three men met at an unlikely setting for such a scandal: the TKE fraternity house is a stately off-campus colonial set among dreary row houses. It is normally filled with Drexel engineering and information technology majors.

Harn attended Drexel between September 1991 and March 1997 and majored in information systems, but like Davis and DaSilva, did not obtain a degree, according to a worker at the school's student administrative office.

Former TKE member Peter Yeomans said preppy attire, khaki pants and topsiders, was in favor then at the fraternity and that Harn stood out because he wore his hair long and at 6 feet 3 he was taller than other members. Harn developed a reputation among younger pledges for going easy on them during hazing rituals, said Paul Zymblosky, 25.

"When I was pledging, he would get me out of some of the, ah, chores I had to do and he'd let me go drink with him in his room," Zymblosky said. "The younger guys liked him cause he didn't really like to ask us to do anything."

He was also more skilled with a computer than almost anybody else there, said former TKE member David Pyne.

After leaving school, Harn worked for Autotote for five years. He "would spend 110 hours a week at Autotote," a co-worker said. He was promoted at least once, according to a former Autotote employee, and he was well-liked by his peers. Harn even met his wife while on company business, during a trip to Peru, said a friend who requested anonymity. They have a 2-year-old daughter.

Davis, who lived in the fraternity's house only for a year, has been running a computer support business out of his house. A Baltimore native, Davis is a big fan of the Orioles. He was the best soccer player on the TKE intramural team and for a period had also been part of the Drexel soccer team, said a family relative.

DaSilva, Harn's roommate for at least part of their stay in the frat house, is also self-employed. He was the TKE treasurer. Former members remember him for wisecracking remarks and his ambition.

In college, DaSilva and Davis were considered less studious than Harn and more fun-loving, said former fraternity members.

Pyne said Harn, DaSilva and Davis were among a small group that often went to local nightclubs or hosted impromptu "mixers" with sororities on campus. Often found together, the group, which also consisted of another TKE member and another Drexel student not associated with the fraternity, was the most outgoing clique at the fraternity, Pyne said. "They were the life of the party."

But Harn was more soft-spoken than others in his circle of friends and more "down to earth" said one member.

"Chris was one of the guys I knew I could always count on," said Pyne, 28. "I knew that if I ever needed anything or had any problems I could go to Chris and he'd be there for me. I can't believe that Chris would ever be part of something like this. The other two I can, but not Chris."

Davis, DaSilva and Harn are due to surrender this morning and will go before a federal magistrate in the early afternoon, the sources said. They will hear the charges against them but will not be required to enter a plea. They probably will be released on their own recognizance after posting bail. The government now has 30 days to obtain an indictment or dismiss the case.

Investigators looking into Davis's bet faced some challenges. It is believed the government lacks absolute proof that Davis and DaSilva didn't choose the winning horses in the races they wagered on. At Catskill, telephone bets are received electronically and the amount of the bet is withdrawn from the bettor's account. If the bets win, the computer then deposits winnings into the bettor's account. But Catskill doesn't use the technology that some sites around the country employ to record wagers when they are punched into a telephone keypad.

Had the recording existed, it could have been compared to Davis's wager and if they were different, it would have proven that the bet was altered. Don Groth, Catskill OTB chairman, said his company is considering using such recording systems in the future.

The key to the case might well be Autotote's computer log files that trace Harn's movements while Davis's and DaSilva's wagers were allegedly altered, security analysts said. According to sources, Autotote's internal investigation found evidence linking Harn to the altered bet. When Harn was questioned by company officials, they said he was uncooperative. On Oct. 31, Harn was fired.

The log files are a record of the movements of Internet Protocol addresses throughout a computer server. IP addresses are the digital equivalent of a phone number, said Doug Rehman, president of the Rehman Technology Services, which performs computer-based investigations for corporations and also provides consulting services to the Department of Justice in computer crime cases.

"Generally, most companies are going to keep access files about who moves in and out of different areas," Rehman said. "The problem that sometimes occurs is when hackers destroy log files."

That is not believed to have occurred in this case. Autotote has turned over log files to police that include Harn's electronic computer footprints on the day of the race, said a source with knowledge of the evidence.

As for the horse racing industry, it has tried to assuage concerns that other wagers have been manipulated in the past and that a similar scandal could happen in the future.

On the day that Harn was fired, Lorne Weil, chairman and chief executive of Autotote's parent company, Scientific Games, had praised his company's "detection system."

"The good news, if there is any, is our detection system worked the way it should have," Weil said in a conference call. "No money was paid or changed hands."

During the call, Weil said Autotote's detection system would have red flagged the alleged alterations to Davis's bet even if they had not raised suspicions.

But DaSilva's bets went undetected until Don Groth, chairman of the Catskill OTB, investigated them in the wake of the Breeders' Cup scandal. Groth, who initially defended Davis, saying there were no signs the bet was illegitimate, spotted the link between DaSilva and Harn.

"Now that we look back, October 5th leaps off the page," New York Racing Association Vice President Bill Nader acknowledged. "But I'll be honest -- it wasn't on our radar screen then."

As for the Drexel trio, Tom Davis, a cousin and former roommate of Derrick Davis, questions why three smart young men would get involved in such a "hare-brain scheme . . . I just can't see this thing going down the way they say it did."

Meantime, the $3 million award awaits a ruling. If the bet is disallowed, the 72 bettors who picked five winners will each collect an additional $35,699.

Staff writer Andrew Beyer, special correspondent John Scheinman and researcher Margaret Smith contributed to this report.

Authorities believe Chris Harn used delay in Autotote's computer system to change bets placed by former fraternity brothers after races had been run.