IMF chief Christine Lagarde has been put under formal investigation by French magistrates for negligence in a political fraud affair dating from 2008 when she was finance minister. Lagarde, who this week was questioned by magistrates in Paris for a fourth time under her existing status as a witness in the long-running saga, said she would contest the decision. Under French law, magistrates place someone under formal investigation when they believe there are indications of wrongdoing, but that does not always lead to a trial.