IMPEACH BUSH

Everyone wants to know who is to blame for the losses paining Wall Street and homeowners.

The answer, it seems, is someone else.

A wave of lawsuits is beginning to wash over the troubled mortgage market and the rest of the financial world. Homeowners are suing mortgage lenders. Mortgage lenders are suing Wall Street banks. Wall Street banks are suing loan specialists. And investors are suing everyone.

The legal and regulatory wrangles could dwarf the ones that followed the technology stock bust and the Enron and WorldCom debacles. But the size and complexity of the modern mortgage market will make untangling the latest mess even trickier. Some cases stretch across continents. Others are likely to involve state and federal regulators.

"It will be a multiring circus," said Joseph A. Grundfest, a professor of law and business and co-director of the Rock Center for Corporate Governance at Stanford. "This particular species of litigation will be manifest in many different types of lawsuits in many different jurisdictions."

The legal battles stretch from Main Street to Wall Street and beyond. Homeowners and subprime mortgage lenders are squaring off in scores of cases that claim some lenders engaged in predatory lending practices and other wrongdoing. Cleveland and Baltimore are pursuing cases against Wall Street banks, saying local residents are suffering because the banks fostered the proliferation of high-risk home loans.

Two questions lie at the heart of many of the cases. The first is whether lenders and investment banks alerted borrowers and investors to the risks posed by subprime loans or securities backed by them. The second is how much they were legally obliged to disclose. "Those are the two issues that are frequently raised," said Jayant W. Tambe, a partner at the law firm Jones Day.

As defaults and foreclosures rise, the various players in the housing market are all pointing fingers at each other. State prosecutors like Andrew M. Cuomo, the attorney general of New York, are investigating whether investment banks that packaged mortgages into securities disclosed the risks to investors and credit ratings agencies. Investment banks, in turn, are accusing lenders and mortgage brokers of shoddy business practices.

"What strikes me here is that this a tainted system from A to Z," said Tamar Frankel, a law professor at Boston University. "Everybody blames everybody else. If you look at what is being said, there isn't one who doesn't blame another and there is half-truth in everything."

Wall Street banks that sold mortgage investments around the world face legal complaints from as far away as Australia and Norway. Lehman Brothers, the Wall Street bank with the biggest mortgage business, is being sued by towns in Australia that say a division of the firm improperly sold them risky mortgage-linked investments. Lehman has denied the charges and has said the unit, formerly known as Grange Securities, acted properly.

Closer to home, members of a New Jersey family have sued Lehman for $4.14 billion, saying the firm steered them into complex securities that have become difficult to sell, Bloomberg News reported Friday. Lehman denied the accusations.

In the United States, Lehman is suing at least six mortgage lenders and brokers like Fremont Investment and Loan and the Fieldstone Investment Corporation, claiming they sold Lehman dubious loans. Lehman claims that borrowers' incomes were overstated, appraisals were inflated and the homes were in poor condition. In most cases, the lenders are fighting the allegations and Lehman's demand that they buy back defaulted or otherwise problematic loans.

In another case, the PMI Group, a mortgage insurer, sued WMC Mortgage, a subprime lender that has stopped making loans, and its corporate parent, General Electric, in California Superior Court. PMI is trying to force the companies to buy back or replace loans that the firm was hired to insure and that it says were made fraudulently or in violation of the standards that the lender said it was using.

According to the lawsuit, a review of loans found "a systemic failure by WMC to apply sound underwriting standards and practices." Reviewing a sample of the nearly 5,000 loans in the pool, Clayton, a consultant that reviews mortgage loans, identified 120 "defective" loans for which borrowers' incomes and employment were incorrect or where the borrower's intention to live in the home was incorrect. WMC offered to buy back 14 loans, according to the lawsuit.

Some of the loans have defaulted, and a trustee's report on the pool of loans packaged and underwritten by UBS, the Swiss investment bank, shows that losses on some defaulted mortgages are as high as 100 percent. As of November, about 27 percent of the loans in the pool were either delinquent 60 days or more, in foreclosure or had resulted in a repossessed home.

PMI is on the hook for losses on defaulted loans, lost interest and principal payments to investors who own a $29.6 million slice of bonds backed by the mortgages. A senior vice president at PMI, Glenn Corso, said he was unsure how much the company had paid out so far.

A spokesman for G.E., Robert Rendine, declined to comment, citing the pending litigation.

Securities lawyers say cases involving mortgage-backed securities, which were generally sold privately to sophisticated institutional investors, are far more complicated than those involving stocks, which were sold publicly to everyday investors. Class-action lawsuits, a favorite tool of plaintiffs' attorneys, will be employed less than they were after the plunge in technology stocks a few years ago because mortgage securities tend to vary in composition and disclosure.

"This is going to be much more complicated to prove, and it's going to be case by case as opposed to class-actions," said David J. Grais, who is a partner at the Grais & Ellsworth law firm in New York and an author of a recent paper on the legal liabilities of credit ratings firms. "This resembles the S&L crisis in the '80s much more than it does the tech bubble in the '90s."

Class-action filings spiked earlier this decade, jumping to 497 in 2001, from 215 the year before, according to Cornerstone Research, which compiles the figures in cooperation with the Stanford Law School. As those suits were resolved, new filings fell to a low of 118 in 2006. But as of mid-December, filings had jumped to 169, with about 32 of the cases related to the mortgage crisis.

Through the end of 2006, settlements in technology- and telecommunications-related class-action suits brought by shareholders totaled $15.4 billion, with more than a third of that coming from one company, WorldCom, according to Cornerstone. Settlements in Enron-related cases have totaled about $7.2 billion so far; the figure does not include Securities and Exchange Commission fines and settlements.

Bringing securities fraud cases has been made harder by recent Supreme Court decisions that favored Wall Street, companies and professionals like accountants. The court ruled earlier this month that two technology vendors could not be held liable for taking part in a scheme designed by a cable company to inflate its revenue. Last summer, in a ruling favoring the company, Tellabs, the court said that securities cases could be dismissed if investors did not show "cogent and compelling" evidence of intent to defraud.

Some plaintiffs are using other legal avenues like the pension law, the Employment Retirement Income Security Act. Under that law, managers who handle pension funds must act in the fiduciary interest of their clients. State Street Global Advisors, which manages pension money, has set aside $618 million to settle claims that the firm invested in risky mortgage-related securities.

Some legal experts say that the recent Supreme Court decisions, which are largely based on cases bought by shareholders, may not have much bearing on the more complex cases that stem from securitization of mortgages.

"There will be a whole new set of claims that deal with the unique nature of the securitization market," Mr. Tambe of Jones Day said. "There will have to be new decisions that deal with those claims and a learning process for the bar and judiciary in those cases."