When Carol Copeland started renovating her World War II-era Stockton home a year ago, things started to happen that were unexplainable, she said.

At first, when she came home to find an empty shelf ripped out of her bedroom wall, she blamed it on faulty carpentry. When she heard the sound of footsteps and her name being called aloud, she brushed it off.

But when she watched as a shot glass collection flew off a shelf in her living room, she said, there was no denying it anymore.

“I always said I’d need to see it before I could believe it,” Copeland said. “Then I saw it, and I can’t really explain it.”

She suspects the house is haunted by the ghost of her aunt, who lived in the home for decades until she died two years ago — and who was very particular about the way she kept her home.

Copeland’s story is a textbook example of a haunting, said Beth Hedricks, director of the new California chapter of the International Society of Paranormal Investigators, based out of the Manteca-French Camp area.

“One of the first things (ISPI investigators) ask is if you are making changes to the house,” Hedricks said. “And the next question they ask is if you’re being treated for any psychological issues.”

That sort of skepticism characterizes ISPI, a research-based group dedicated to seeking out things that go bump in the night. Once their skills are honed, members respond to calls from the public about suspected hauntings.

Unlike some ghost-hunting groups, the group steers clear of psychics. Instead, members base their investigations on science and history, Hedricks said.

“I go into every location as a skeptic,” she said. “Probably eight out of 10 hauntings are easily explained. I want to find the two that aren’t.”

The way to properly investigate a haunting is to try to disprove it, she said. Investigators tackle practical matters first, looking for outside factors that could look or feel like a ghost.

Carbon monoxide leaks, for example, are often behind suspected hauntings. The deadly gas can make people’s hair stand on end and make them see things when nothing is there, Hedricks said.

Research comes next, when — clad in the society’s work shirts and toting cameras, recording equipment and thermometers to document temperature shifts — investigators collect evidence to determine whether a ghost might be lurking about.

Looking into the history of the house and its inhabitants helps them paint a fuller picture. Still, at the end of the day, Hedricks is left with as many questions as answers.

“I don’t care how many years you’ve been doing this,” she said. “It’s all theory. You don’t know until you’re on the other side.”

For now, new members are learning the ropes through monthly meetings and outings. They’re also embarking on a month-long research project about a person buried in Park View Cemetery.

At the group’s meeting Saturday, May 12, no members wore “gothic” clothes or trench coats, Hedricks pointed out, laughing.

“It’s hard to get beyond that mystique and show that we’re all normal, down-to-earth people that are curious about something,” she said.