Metro has won a Maryland court battle reinforcing its claim that it is immune as a government agency from slip-and-fall lawsuits.

The Maryland Court of Appeals ruled that the transit agency was not liable for its maintenance decisions in two cases stemming from riders slipping on wet floors at Prince George's County Metrorail stations.

"We are pleased with the decision and consider it to be within well-established law," said Metro spokeswoman Caroline Lukas.

Federal lawsuits involving Metro, by year*
2002: 32
2003: 30
2004: 37
2005: 29
2006: 24
2007: 42
2008: 38
2009: 54
2010: 48
2011: 55
2012**: 62
*Includes all cases involving the transit agency as a party, whether as a plaintiff or defendant
**Year to date

The agency is a frequent target of lawsuits, and the numbers have grown in recent years. At least 62 suits involving the Washington Metropolitan Area Transit Authority have been filed this year in federal courts, more than any year in the past decade. But the latest court decision could dissuade some riders from ever filing cases.

"It means WMATA slip-and-fall cases are going to be virtually unwinnable," said Ron Miller, a personal injury lawyer whose firm handles cases in Maryland and the District. "We wouldn't take the case, no matter how good."

While the decision took place in the Maryland court system, it likely would influence courts in Virginia and the District, as well, Miller said.

The issue hinges on when Metro can claim, like other government agencies, it isn't liable for injuries. The transit agency formed by Maryland, Virginia and the District says the protections those governments hold were passed along to Metro as "sovereign immunity" when they formed the agency. But Metro does not have immunity in all things.

Miller, who blogged on the decision on the Maryland Injury Lawyer Blog, said accidents involving buses and trains are still fair game for lawsuits.

The state's highest court said immunity depends on whether the suit stems from a governmental decision grounded in policy, such as when to mop floors, or was part of a so-called proprietary function that involves discretion, such as failing to stop a speeding bus for a red light, causing a crash.

The first case dates to 2007, when Veronica Tinsley slipped on a wet platform at the Cheverly station on the Orange Line and broke her ankle. She argued that the platform had been mopped during rush hour, contrary to an agency rule to wait until after 7 p.m., and no signs warning riders were placed there. A jury sided with her and awarded her $64,213.78 in damages.

The second case addresses a fall by Kim Hodge in February 2010 at the Prince George's Plaza Metro station on the Green Line, when she slipped in a pool of water. The agency said the water was due to melted snow tracked in by other riders, and crews had placed yellow warning cones around the area. A jury awarded her $18,945.77.

Others have lost on similar terms before. Following rounds of court battles, a family ultimately lost its suit against Metro after its son, Richard Smith, had a fatal heart attack in 1998 while climbing up a downed escalator on a hot July day at the Bethesda station.