A federal judge has sentenced former Blackwater security guard Nicholas Slatten to life in prison for his role in a 2007 shooting that killed 14 Iraqi civilians and wounded 17 others.Three other guards Paul Slough, Evan Liberty and Dustin Heard were each sentenced to 30 years and one day in prison for charges that included manslaughter, attempted manslaughter and using firearms while committing a felony.U.S. District Judge Royce Lamberth announced the sentences after a day-long hearing at which defense lawyers had argued for leniency, and prosecutors asked that those sentences, the minimums mandatory under the law, be made even harsher.