"Fraud and potential criminal conduct were at the heart of the financial crisis," Senator Ted Kaufman (D, Del) said in a speech last month on the Senate floor.

Look no further than the civil fraud charges the Securities & Exchange Commission has brought against Goldman Sachs (NYSE: GS) to understand some banks' securities dealings at the core of the financial crisis. The SEC alleges that the firm misled investors about securities known as collateralized debt obligations. The lawsuit doesn't just have possible repercussions for Goldman Sachs, but also potentially for other brokerage houses that engaged in similar trades or possible misrepresentation of their roles in marketing mortgage-backed securities deals. Federal prosecutors have issued civil subpoenas and launched preliminary criminal probes for several banks: JPMorgan Chase (NYSE: JPM), Deutsche Bank (NYSE: DB), and UBS (NYSE: UBS) among them, according to The Wall Street Journal.

Senator Kaufman has taken a lead role in tackling financial fraud. Last year he sponsored and helped pass the Fraud Enforcement and Recovery Act, and he recently has proposed a couple amendments on fraud. Among those proposals, the amendments -- if passed -- would impose fiduciary duties on all registered brokers in an effort to end conflict of interest; they also increase law enforcement resources to find and prosecute financial and securities fraud.

I sat down with Senator Kaufman to discuss cracking down on fraud on Wall Street. He says we need to get the regulators back on the beat, get Wall Street on board, and write clearer laws. 

This is one of three segments of my interview with Senator Kaufman. For Senator Kaufman's take on the financial reform bill click here. For the Senator's take on the flash crash click here.

Fool contributor Jennifer Schonberger does not own shares of any of the companies mentioned in this article. You can follow her on Twitter. The Motley Fool has a disclosure policy.