The Kentucky Derby’s winning horse has only lost its title once before in history—and it wasn’t a case of officials immediately disqualifying a horse that finished first, as with Maximum Security in the 2019 race. In this case, a horse named Dancer’s Image held the proverbial crown for nearly three days before the Churchill Downs disqualified him for drugs in 1968.

Ironically, the specific drug in the stallion’s system is something most horses use today in the famous race.

Dancer’s Image was a gray thoroughbred who swept to a first-place finish at the Kentucky Derby on May 4, 1968, a full 1½ lengths ahead of any other horse. His owner Peter D. Fuller attended the victory party that Saturday night assured that he had just won $122,000 in prize money (that’s roughly $890,000 in 2019 dollars). While the festivities were going on, however, a chemist was performing a standard procedure: testing the urine of the winner and one other randomly selected horse from the big race.

The chemist was mostly looking for performance-enhancing drugs like heroin and cocaine. Because these both act as stimulants in horses (though heroin acts as a depressant in humans), the drugs had become a problem in horse racing during the 1930s, says Milton C. Toby, author of Dancer’s Image: The Forgotten Story of the 1968 Kentucky Derby.

“At the time, Kentucky had what’s called a zero-tolerance policy for prohibited medications,” Toby says. “Which meant that even the smallest trace of this drug and the other prohibited medications in a horse’s system was grounds for disqualification. It didn’t matter how much it was, there just had to be at least a trace.”

One of the drugs on the prohibited medications list was phenylbutazone, often referred to as “Bute,” which acts as an antihistamine and pain-reliever in horses, similarly to how aspirin works in humans. It isn’t a steroid or stimulant that affects a horse’s performance as drastically as heroin or cocaine, and many horses used it during training for the 1968 Kentucky Derby. Still, they weren’t supposed to have any of it in their systems by the time they raced in Louisville, and the chemist found that Dancer’s Image did.

It later came out that a veterinarian had given Dancer’s Image some phenylbutazone about a week before the race. Most horses would have gotten the drug out of their system by then, but it seems Dancer’s Image’s body didn’t process it as quickly. Because of the zero-tolerance policy, racetrack chemists only tested for the presence of certain drugs, not the amount that was in a horse’s body. So it didn’t matter whether Dancer’s Image had a lot of phenylbutazone in his system or just trace amounts from a previous dose—he was going to be disqualified.

Officials at Churchill Downs didn’t discover the drug test results until Monday when they received the chemist’s report. They spent the day tracking down the horse’s trainer, Lou Cavalaris, to tell him that Dancer’s Image had tested positive for phenylbutazone. This meant the horse would lose its first place title and be moved to last place. The next day, Churchill Downs made the news public. The new winner was Forward Pass, who’d come in second behind Dancer’s Image.

Fuller sued over this decision, and the court cases dragged on for nearly five years while the first-place prize money sat in an escrow account. “He had a lot of money, and he was the first person to actually make a serious claim that the tests were inappropriate and that the racing chemist was incompetent,” Toby says.

A state judge actually ruled in Fuller’s favor, but the victory was short-lived because the Kentucky State Racing Commission appealed and won. Fuller gave up the legal battle in 1973, and Churchill Downs was finally able to award the prize money—plus the interest it gained in escrow—to Calumet Farm, which owned Forward Pass.

“It’s one of the most important administrative law decisions in racing, because it really established the authority of a racing commission,” Toby says.

Then the Kentucky State Racing Commission did something surprising. Less that a year after winning the lawsuit about its ability to disqualify a horse for taking phenylbutazone, the commission approved that same drug for use during the Kentucky Derby. Toby isn’t sure why the commission made this decision, but it may have had something to do with the debate around Fuller’s lawsuit, and whether phenylbutazone really needed to be on the list of prohibited medications along with harder drugs.

“There’s a question about whether it is performance enhancing,” Toby says. “If a horse is sore, it gets a dose of Bute a few hours before the race. Then he’s not going to be feeling bad and he probably will run better. So in that context it is performance enhancing.” At the same time, many feel “it isn’t fair to equate Bute with some of the real performance-enhancing illegal drugs. Using Bute isn’t an attempt to dope the horse at all.”

Because the disqualification of Dancer’s Image appeared so technical—not to mention the fact that phenylbutazone became acceptable at Derby races just six years later—Fuller suspected there was something else going on. After Martin Luther King, Jr.’s assassination a month before the 1968 Kentucky Derby, Fuller had donated the prize money from a previous race to Coretta Scott King, King’s widow. After Dancer’s Image was disqualified, Fuller wondered if someone unhappy with his support of the Civil Rights Movement had sabotaged his victory.

Fuller, a white man from New England, had been viciously criticized before the race for his full-throated support of civil rights. Fuller had known King when he was alive, and had protested against housing discrimination in Louisville during the 1967 Kentucky Derby. In the weeks before the ‘68 Derby, people sent him angry letters and death threats, and someone set one of his stables in New Hampshire on fire. In addition, there were reports of white people openly referring to Dancer’s Image by a racist slur.

Fuller asked Churchill Downs if he could have extra security for Dancer’s Image in light of this harrassment, but the racetrack denied his request. So could someone have slipped the horse some extra phenylbutazone before the race? Possibly. Yet it’s just as likely that the horse still had some in his system from the week before. In any case, the drug is no longer against the rules, and most Kentucky Derby horses—in fact, most American racehorses in general—likely have it in their system when they line up at the starting gate.