Federal prosecutors may be about to run out of time to file criminal charges against Wall Street participants for their role in the financial crisis. Charges for most federal offenses, including securities fraud, must be filed within five years of the offense, experts say. The subprime lending that played a significant role in the crisis reached its peak about five years ago ? in 2007. Thus, the statute of limitations is already likely to be an issue in cases that prosecutors may file, if any.