The former Liberian president and convicted war criminal Charles Taylor has been sentenced to 50 years in prison by an international court in The Hague.
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The US president, who has not visited the UK since being elected, is reported to be planning a summer trip to Britain.
Mack entered her plea in federal court in Brooklyn. The judge refused a request by her lawyers to release her without bail.
Officers investigating a reported break-in on Friday found 22-year-old Roger Alvarado asleep in the pop star's home in Tribeca.