SAN FRANCISCO (Reuters) - Lenders snarled in the legal thicket over shoddy U.S. foreclosure procedures have so far avoided national class action lawsuits from homeowners, largely because borrowers cannot demonstrate economic harm, according to plaintiff lawyers.

Several large plaintiff firms circled around banks when reports of problems with foreclosure affidavits snowballed in late September.

But as servicers like Bank of America Corp, Ally Financial and JPMorgan Chase attempt to resolve a 50-state probe into their practices -- and other legal challenges -- big class action lawyers have taken a pass on diving into the mess.

“We looked at this up one side, down the other,” Joseph Cotchett, of Cotchett, Pitre & McCarthy, said on Wednesday.

Ultimately, the firm decided it would not file suit over the affidavits, Cotchett said, because most borrowers are actually behind on their payments.

That makes it too difficult to make a claim for serious damages, he said. “It’s about as basic as that,” Cotchett said.

A public furor erupted in recent months over whether banks cut corners in the foreclosure process with so-called “robo-signers” of legal documents used to justify taking homes. Servicers briefly halted foreclosures and evictions as state and federal regulators announced investigations.

Banks have disclosed some legal challenges from homeowners, but the class action lawsuits they are facing have not been national in scope.

In defending one Indiana class action, Bank of America has echoed the conclusion reached by some plaintiff lawyers in arguing that the borrower cannot show harm because they would have lost their home anyway.

Plaintiff attorneys are usually paid a portion of the damages they recover.

Some plaintiff lawyers who have devoted resources to the issue haven’t walked away yet. Bruce Simon, with Pearson, Simon, Warshaw & Penny, said this week that his firm still intends to file a national class action.

And Lieff Cabraser Heimann & Bernstein’s Eric Fastiff said his firm is still examining the issue. “Investigations take time,” he said.

Andrew Friedman of Cohen Milstein said he strongly believes many foreclosures were done improperly.

But getting a judge to certify a national class action is difficult, he said, because homeowners have wildly varying circumstances in terms of their relations with servicers.

That, combined with the damages issue, makes a class action tough.

“I’ve looked at it pretty seriously, but I keep running into the same buzzsaw,” Friedman said.