MIAMI (Reuters) - A lawyer for a defendant in the Argentine "suitcase scandal" said a U.S. government witness has sworn that Venezuelan President Hugo Chavez was personally involved in the affair, according to a U.S. court filing. The government witness, Carlos Kauffmann, pled guilty in March to U.S. charges arising from the seizure of $800,000 in a suitcase in Buenos Aires and agreed to testify against former associate Franklin Duran in exchange for lighter punishment. U.S. prosecutors have indicated that they had been told the $800,000 was intended for the election campaign of Cristina Fernandez de Kirchner, the former first...