PHILADELPHIA -- A group of Philadelphia police officers spends its free time investigating claims of disorderly conduct, harassment and criminal mischief, knowing the cases don't have a ghost of a chance of making it to court.
Still, the officers set up video cameras at each scene and spend hours poring over evidence, looking for just one shadow, listening for just one voice.
By day, the officers protect the mayor, police headquarters and the streets, but by night, they patrol the paranormal as members of the group Olde City Paranormal.
With the success of reality shows like "Ghost Hunters," interest in paranormal investigations is growing. In Pennsylvania alone, more than 300 paranormal investigation groups exist, according to the Paranormal Societies website.
Several of the groups claim law enforcement officers as members or founders, including Olde City Paranormal, co-founded by Philadelphia police Officer John Levy, who works security at police headquarters, Eighth and Race streets.
Officer Levy's wife, Amanda, an officer in the 24th District in North Philly, is also on the team, as is Officer George Feinstein, who works in Mayor Michael Nutter's detail.
While many question the existence of paranormal activity, Officer Levy became interested in it after watching ghost-hunting shows and having what he described as a firsthand experience with a ghost.
He had stopped by his mother's empty house while on patrol one night to use the rest room.
Out of the corner of his eye, he said he saw a figure walk into the room where his grandfather used to sleep.
"It was my grandfather. My grandfather has been dead since '87, '88," Officer Levy said.
"There was no doubt in my mind it was him -- his height, his walk, his stature -- it was him."
In 2009, Officer Levy joined with Steve Rotondi, a welder and a tattoo artist, to found Olde City Paranormal. They estimate they've done more than 30 investigations in their off time.
"We have been so fortunate, too," Mr. Rotondi said. "I would say in 80 percent of the cases, we've gotten stuff that makes you go, 'What?' "
But, Officer Levy said, one of the first things he tells those who report a paranormal occurrence is not to be offended if he doesn't substantiate their claims.
"I don't expect to go into anything and find anything, and I don't consider myself a ghost hunter," Officer Levy said.
"We're investigators. As with my job in the police department when I was on the street, we investigate."
Their investigations have taken them to private homes and businesses, a shuttered nursing school and historic landmarks. They never charge for their services.
"How do you justify charging for something like this? What's your price list? If you find a demon, it's so much?" Mr. Rotondi said.
"Every single part of this is speculation. Nobody knows the answers about any of this stuff."
They do have events in which the public can pay to tag along on an investigation, but the fee is donated to the venue.
The men estimate they've raised more than $27,000 for various sites, including about $2,000 recently at Graeme Park in Horsham, Montgomery County, where written accounts of hauntings date from 1801, said Beth MacCausland, president of Friends of Graeme Park.
Ms. MacCausland said that of all the paranormal groups to visit Graeme Park, Olde City Paranormal was the most professional.
"It's not a carnival or a circus. They take their ghost-hunting seriously, but they take the park and its history seriously as well," she said.
"You just see some of these groups make up stories, but never with John's group."
Rob Fabiani, a Chicago-area cop who starred on A&E's "Paranormal Cops," said cops who moonlight as paranormal investigators are often held to a higher standard.
"Being the police, that just in general raises the bar," he said.
"If I was a plumber, I could lie through my teeth and go back to work tomorrow. As policemen, we don't have the luxury of being reckless. We're held accountable for what we say."
Officer Levy said he doesn't see anything "super or special" about officers who conduct paranormal investigations, but Officer Fabiani disagreed.
"There are numerous, gigantic differences between a police officer doing paranormal investigations and John Q. Public," he said. "We understand the importance of accountability, credibility, chain of custody, securing a scene, obtaining evidence and conducting background investigations of those who contact us."
Officer Levy said he takes care to look into the background and family situations of people reporting paranormal activity. He questions subjects about drug and alcohol abuse and family issues.
"When it comes to our private-home investigations, when there's families and kids involved, it's very serious to us," Officer Levy said.
"Nobody wants to see kids scared in their own house."
Sometimes, the investigators will uncover normal causes behind what otherwise appears to be paranormal activity.
Around Christmas last year, they conducted an investigation at a home where the residents reported a snakelike demon in the house with a certain smell.
Not only did Officer Levy and his team discover that the family had domestic issues, but they uncovered a crack in the foundation of the home, a bad mold problem and a major gas leak on the property.
"That house could have blown up," he said.
But not every case can be explained. One of the favorite haunts of Olde City Paranormal is Temple University Hospital's old nursing school.
Using audio recorders, the investigators have obtained clear electronic voice phenomena, known as EVPs.
They've recorded a little girl's voice saying "Mommy, I'm here," and a strange man's voice saying "Aren't you cold?"
Aside from audio and video devices, the investigators use a laser grid pen, which produces a pattern that, when disrupted, could signal paranormal activity.
They also use what's called a modified K2 device, which is an instrument that combines an infrared thermometer and an electromagnetic field, or EMF, tester.
"EMF fields are real big in paranormal investigation because in theory, that's what spirits use," Officer Levy said. "They're energy, and they use energy to manifest themselves to do whatever it is they do that cause people to call us."
Officer Levy has no qualms about talking with his colleagues about his unusual hobby and says being a cop has given him thick enough skin to handle the ribbing.
"You break stones, you get your stones broken," he said. "But what I say to these people is, 'Why don't you come out with me?'
"And they're always like, 'Nu-uh.' "state