New research by Edward Pinto, a former chief credit officer for Fannie Mae and a housing expert, has found that from the time Fannie and Freddie began buying risky loans as early as 1993, they routinely misrepresented the mortgages they were acquiring, reporting them as prime when they had characteristics that made them clearly subprime or Alt-A.  
 
In general, a subprime mortgage refers to the credit of the borrower. A FICO score of less than 660 is the dividing line between prime and subprime, but Fannie and Freddie were reporting these mortgages as prime, according to Mr. Pinto. Fannie has admitted this in a third-quarter 10-Q report in 2008.  
 
An Alt-A mortgage is one in which the quality of the mortgage or the underwriting was deficient; it might lack adequate documentation, have a low or no down payment, or in some other way be more likely than a prime mortgage to default. Fannie and Freddie were also reporting these mortgages as prime, according to Mr. Pinto.  
 
It is easy to see how this misrepresentation was a principal cause of the financial crisis.