US politicians, including President Barack Obama, have been calling on Europe to fix its debt crisis, amid fears it will have a negative impact on the fragile US economy.

But there is evidence that the Greek debt crisis began on Wall Street, at the hands of one controversial US bank.

According to former financial regulators, Goldman Sachs made a dozen derivative deals with Greece a decade ago, writing its debt off its balance sheet for a number of years.

They also say that Goldman and Greece were not the only ones working such transactions.

Al Jazeera's Patty Culhane investigates the morality versus legality of who is to blame for the financial crisis that is scaring the world.