"Oh my God, now we’re all going to get a black eye," was Jacki Mari’s first thought when she heard that a false tip from a psychic had led law enforcement officers on a fruitless search for a mass grave in East Texas on Tuesday night.

Mari, also known as Sherlockjackie, has, by her own reckoning, helped solve more than 400 murders and missing persons cases around the world — all without leaving her office outside Chicago. Her own psychic powers — she calls it "extrasensory intelligence" — told her that the informant’s tip was spurious, Mari said, even before the news media frenzy over the search in Texas died down and the spokesman for the sheriff’s department confirmed that no bodies had been found in Hardin, northeast of Houston.

"My first feeling was that something did happen," Mari said, "but I didn’t see a bunch of bodies laying around or dismembered." Besides, she added, "I would never call the police department and say, ‘Hey, I’m a psychic and I know what’s what."’

The psychic’s phone call to the Liberty County Sheriff’s Department — which summoned not only sheriff’s deputies but also FBI agents, Texas Rangers, cadaver-sniffing dogs and an army of news media personnel — was only the latest milestone in a long and uneasy relationship between law enforcement agencies and people claiming extrasensory powers.

Despite Hollywood’s romance with the notion of clairvoyants solving crimes, a passion that spawns television shows like "Medium" and "Psychic Detectives," the use of psychics by police departments is occasional at best. In one survey of the nation’s 50 largest police departments, published in the magazine Skeptical Inquirer, 65 percent of the departments responded that they had never made use of psychics. And those that had were quick to play down the official nature of the association.

"This was on my own volition and does not reflect policy of the Chicago Police Department," one chief of detectives said, telling the researchers that he had called upon the services of a psychic twice in investigations.

Yet clairvoyants have played a role in some of the country’s most notorious murder cases, including the John Wayne Gacy murders in Illinois, which Mari claimed she helped solve. And when leads are scarce, even the most skeptical detectives may find themselves hoping that a psychic’s intuitions might turn out to be useful.

"I’m a pretty down-to-earth guy," said Chief Jack L. Rinchich, president of the National Association of Chiefs of Police and a retired police officer, "but if you’ve got a potential case and you’ve exhausted all your tangible leads and someone comes up with a suggestion such as this, it doesn’t hurt to check it out."

How accurate the insights offered by psychics really are is a subject of dispute. Rinchich, noting that many police officers are skeptical, said that he could not discount the possibility of "a spiritual element that we can’t identify."

But Joe Nickell, a former stage magician and private investigator who has written extensively about extrasensory abilities in order to debunk them, said there was no scientific proof for the validity of psychic powers. Instead, he said, a psychic’s supposed success in solving a crime is often a result of people "retrofitting" the psychic’s clues to fit the facts afterward.

In one case, Nickell noted, in 1983, a psychic named Greta Alexander offered the police in Alton, Ill., a series of clues to solving the murder of 28-year-old Mary Cousett, among them that her body would be found near a church. After the skeletal remains were found, Alexander received credit, even though many of her clues, including the proximity of the church, were incorrect.

A psychic’s hunches sometimes set off searches that waste valuable time and resources, as in the Texas case, Nickell said. In 1968, he said, the police in Nutley, N.J., spent hours digging up a drainage ditch after a psychic, Dorothy Allison, claimed that a missing boy was buried there.

In Texas, the Liberty County Sheriff’s Office said in a statement on Wednesday that it was still trying to identify the woman who called in the anonymous tip, claiming that she was psychic and that up to 30 bodies, including those of children, were buried on the property in Hardin. When officers investigated, they found blood on a fence and smelled what they thought might be rotting bodies, the statement said. But after a search warrant was obtained, there were far less gruesome explanations for both — the odor was apparently from rotting meat.

Judge Craig McNair of Liberty County said that he was skeptical about psychics, but that the sheriff’s department was obliged to investigate the tip and to search further once the blood and the bag were found.

"You have to be careful in this day and age," he said. "Terrible things happen."