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 .
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 .