Earlier this month, Laurel Park scheduled a race for amateur jockeys, and one of the participants was a rider named Carlos Castro. He went through the necessary formalities -- securing a Maryland license and getting fingerprinted -- before losing aboard a long shot. Afterward, as Castro and a tableful of guests lunched in the Laurel dining room, Pierre Bellocq, the founder of the amateur rider program, stopped by and snapped a photograph of the group.

Bellocq was pleased with this recent addition to his Amateur Riders Club of the Americas. In three races to date, Castro had demonstrated that he possessed talent. Moreover, he wasn't just another member of the well-bred horsey set. "We didn't want to make this club an elitist group of snobs," Bellocq said. "We wanted it open not just to rich kids but to everybody."

Bellocq may have felt a momentary rush of pride Saturday, as Castro guided a horse named Cop a Kiss to victory in an amateur race at Aqueduct. He looked so good in the saddle that track announcer Tom Durkin commented on his "very professional ride."

Indeed, it was too professional. Castro isn't an amateur; he is a former jockey and exercise rider. He isn't even Carlos Castro; his name is Angel Monserrate Jr. He was banned from New York Racing Association tracks in 1995.

Nearly an hour after Saturday's race, as Monserrate was being led out of the track in handcuffs by NYRA security and taken to a police precinct where he was charged with criminal trespass and tampering with a sporting event, stewards declared the event no contest. Bettors who had wagered on the winner got only a refund instead of an $8.80 payoff. Those who bet on losers were entitled to a refund -- if they hadn't thrown their tickets away. Winners and losers alike were cursing both the stewards and the amateur riders' program.

There is no evidence that Monserrate had any sinister motives for his deception. He wanted the thrill of riding at a racetrack again, and apparently found a way through the back door with ARCA.

Bellocq, who had ridden in amateur races in his native France, has spent the past 10 years promoting such events in the United States. He is best known by the name Peb, as he signs the Daily Racing Form cartoons that have made him an admired figure in the sport. Because of his prominence and popularity, he was able to persuade many racetracks to offer races for amateur riders -- even if the public was less than enthusiastic about betting on jockeys whose only distinguishing characteristic was their relative lack of talent.

Another amateur rider had recommended "Castro" to Bellocq, who said the applicant produced various documents identifying him by the false name. "Castro" was fingerprinted before he rode in New Jersey and Maryland. Why didn't the fingerprinting disclose the deception? Paul Berube, president of the Thoroughbred Racing and Protective Bureau, said that "there can be a delay in processing the prints . . . or possible other administrative loopholes." But he said amateur riders are subjected to the same degree of scrutiny as professionals.

If the impostor had stayed out of New York, he might have continued his deception. When he showed up Saturday at Aqueduct -- where he had worked as an exercise rider before being ruled off -- a trainer recognized him as Monserrate and reported this information to the stewards. When Monserrate's mount won, the stewards didn't post the inquiry sign or otherwise inform bettors that they ought to hold all tickets. But after an hour had passed and they had verified the rider's true identity, the stewards decided that "in fairness to the public" the race should be no contest.

It's debatable that this is fair. Most bettors were wagering with little knowledge of the riders' skills anyway; would anybody have been swayed by the fact that Angel Monserrate Jr. was riding, not Carlos Castro? And what would the stewards have done if Just a Cop had finished second? Or finished out of the money?

Officials have not yet announced whether purse money will be paid to the winning owner, Buzz Beler, proprietor of the Prime Rib Restaurant in Washington. Beler said yesterday that the NYRA had picked the rider for him, and that he shouldn't be penalized for others' errors. "Why didn't they just make the race official and go on about their business?" he asked, echoing the sentiments of most horseplayers.

New York's handling of this incident is open to question, but most questionable of all is the industry's decision to permit amateur races in the first place. What's the point? Aside from Monserrate/Castro, most of these riders are members of the affluent horsey set, and these races exist so that they can fulfill their fantasies of competing at a racetrack. This would be a harmless indulgence if no wagering were involved, but bettors frequently are enraged when they lose their money because of an amateur's incompetence.

Saturday's events point to the larger problem involving these amateur races. The thoroughbred industry depends on public confidence in its integrity, and it has to control its product. If an outsider approaches a racetrack and says, "I'd like to select and provide all the jockeys for certain of your races," such a proposal ought to elicit worry and skepticism, even if Mother Teresa is making it. While the industry has nothing to gain from these amateur races, it has a lot to lose if one of them goes awry.