Doctor, lawyer, wheelchair user: It's the same person. And he's filing disability lawsuits by the bundle.

David Ketroser has a medical degree, a law degree and a habit of suing people.

In recent months, Ketroser — a pain management specialist who uses a wheelchair due to multiple sclerosis — has filed nearly 100 lawsuits in Minneapolis and the west metro suburbs, alleging violations of the Americans with Disabilities Act and the Minnesota Human Rights Act.

He's been demonized by some local business owners and civic leaders, who accuse him of literally engaging in drive-by litigation. They say he scouts businesses from his car, spots violations of handicapped parking rules, and sues them without even trying to go inside.

Then he asks the businesses to fix their violations and pay him $2,000 for his time and trouble.

"It's basically blackmail," said Colin Brown, a director of the Hopkins Historical Society.

Ketroser's one-man crusade offers a window into society's ongoing struggle to integrate disabled people into everyday life. Although the Americans with Disabilities Act was passed in 1990, it's still a target of criticism from business groups who say it sets unrealistic and costly standards for compliance, especially for small businesses.

Just last week, Gov. Mark Dayton signed a package of business-friendly amendments to the Minnesota Human Rights Act, which governs the legal rights of the state's disabled residents.

The amendments require people suing for accessibility under the Human Rights Act to detail each specific violation, rather than make a blanket complaint. Plaintiffs no longer may demand money when they file their complaints, and they must give their targets at least 30 days to respond to the complaint.

"We worked with the Minnesota Chamber of Commerce to pass a bill that at least slowed down this egregious drive-by litigation," said Deb McMillan, director of government affairs for the TwinWest Chamber of Commerce, which represents 10 west metro suburbs. "There's no room for abusive lawsuits."

The author of dozens of those so-called abusive suits said he shouldn't be criticized merely for seeing to it that businesses observe the law.

"The very fact that I could sue as many people as I sued tells you that the law is just being ignored," said Ketroser, 64. "And I don't think it's because they have animus against people with disabilities. I think we're invisible."

With accessibility laws widely ignored after more than a quarter-century on the books, he said, lawsuits are the only way to force businesses to take the issue seriously. If he simply complains to a business about a violation, he said, "I've talked to one business and she fixed it."

"But if I sue a few businesses, then a lot of people fix it. I get leverage."

There are a handful of people like Ketroser in every state, said Joseph Windler, a Minneapolis attorney who defends businesses against accessibility lawsuits.

"This is a nationwide issue," he said.

Some attorneys have formed disability groups specifically for the purpose of filing lawsuits, Windler said, calling such groups "blunt objects" to exploit loopholes in the federal law.

Last week, Windler met with about 25 Hopkins business owners and civic leaders to discuss disability lawsuits and how to deal with them.

"Hopkins and St. Louis Park are kind of in the hot zone right now," Windler said, noting that Marshall, Minn., and Mankato also have been the targets of accessibility lawsuits.

Ginny Mulvaney, who owns a swimming pool and spa business in Hopkins, said she's being sued by Ketroser for a handicapped parking violation.

Although her business had a properly marked handicapped spot, it didn't have a sign identifying the spot. Mulvaney said she put up the sign within 48 hours, got a lawyer and will fight Ketroser's suit.

"I want to stop the guy," she said. When it was pointed out that she might pay her attorney more than the $2,000 Ketroser demanded, she said: "I don't care."

Despite his wheelchair, Ketroser said he doesn't really see himself as disabled, noting that his disease hasn't yet affected his ability to keep up his medical practice. He's also pursuing a master's degree in bioethics at the University of Minnesota.

"But I see myself as someone who has insight into being disabled, and I'm in a position to fix it for other people," he said. "That's what turns me on."

Ketroser has a history of taking action when he perceives wrongdoing. In 2012, the Mayo Clinic agreed to pay $1.26 million to settle a federal lawsuit that accused it of billing the government for thousands of lab tests that were never performed.

The whistleblower in that case: Dr. David Ketroser.

"It's a character flaw," he said of his need to get involved. "When I was young, I used to describe it as, I had a really hot spider burning inside me. I could walk through walls."

What would Ketroser say to a business owner who dreads seeing him on their doorstep — or, perhaps more accurately, in their parking lot?

"If they're violating the law, they're going to be in constant danger of being sued," he said, leaning forward intently. "And I'm probably their best option."

John Reinan • 612-673-7402